A new procedure has been implemented for plotting the PLASTIC proton density,
velocity, and temperature data in the daily
pages. This procedure uses preliminary data from the PLASTIC science telemetry
stream to significantly reduce the noise compared with the original real-time
beacon data. These improved plots are available 1-3 days after the observation
date, while the real-time plots are unaffected. Please note that these
improved plots are from preliminary data, and do not necessarily represent the
final instrument calibration.
September 13, 2023
During STEREO Ahead's close to approach to Earth in August 2023, it underwent a
slow rotation to keep the high gain antenna pointed toward Earth. This
affected our ability to produce clean COR2 and HI1 images for the browse pages.
However, for the most part, running difference images were mostly unaffected,
and we encourage users to use these images during this special period.
The SECCHI COR1 telescope experienced a problem with its polarizer wheel
mechanism that degraded images starting late on August 16 and continuing
through 08:16 UT on August 26 when a parameter change fixed the problem.
June 30, 2023
The orbit tool for STEREO-A's close approach
to Earth in August 2023 now includes links to additional resources for this
period. Some are links to real-time data, while others will correspond to the
date selected in the tool once that date has been reached. In the meantime,
those links default to the current date.
September 13, 2022
The S/WAVES data have a new organization,
with a more logical directory structure, and improved filenames.
and Behind trees contain the data in
ASCII and IDL format, while daily summary plots can be found
under Both. The original data and plot
files are archived under old.
September 6, 2022
On day 243 (Aug 31), the IMPACT team performed real-time commanding to adjust
the HET low gain thresholds on Ahead. The SEP-Central Processor reset after
receipt of the first command at 243-13:50:52z. The team completed the SEP
recovery by DOY 245-1513z (Sept 2). During that period, data from SEP are
August 29, 2022
A new tool for tracking the STEREO Ahead spacecraft during its close approach
to Earth in August 2023 is now available.
Along with the STEREO spacecraft, the locations of other nearby spacecraft at
the Lagrange L1 are also shown.
The solar wind plots for PLASTIC have been reprocessed with the new software
back to 9 April 2020. This improves the density and velocity parameters in the
plots. Velocity data are currently unavailable due to the present high
June 30, 2020
The realtime beacon telemetry from the PLASTIC instrument is being processed
with new software which improves the density and velocity parameters in the
realtime product. Velocity data are currently unavailable due to the present
high instrumental background.
The PLASTIC team reports: All PLASTIC systems are behaving well, except there
is a high background count rate, which seems to have a locus toward the
non-solar wind side of the instrument (which we call the WAP or Wide Angle
Partition), which includes the ram direction. While we continue to monitor the
background rates, we are gradually increasing the post acceleration voltage,
alternating with short windows of exercising the entrance system. Our first
entrance system test last week showed a solar wind peak, but with a low signal
to background ratio. We expect the signal/background ratio to improve as 1)
the PAC increases (which increases the efficiency of the solar wind detection)
and 2) the background decreases (as it is doing exponentially). We are going
slow, using only the longer command sessions so that we can watch each step in
real time. We have some composition measurements of the background rates, that
indicate the presence of H+ and H2+ inside the instrument.
December 11, 2019
PLASTIC suffered a high voltage anomaly on December 5, 2019. To correct the
anomaly, the PLASTIC instrument was powered off on December 9, and powered back
on December 11. The instrument is still in the process of being recovered to
full operating mode. In the meantime, the PLASTIC data should be considered to
August 8, 2019
As per NASA directive, the STEREO ftp server has been deactived. All
data previously available via ftp can be downloaded via https from the
same locations under the pub
subdirectory on this server.
A new procedure to
update SolarSoft is under development. Some additional steps are still
needed to allow batch updates, but users can use this procedure to update
by hand now.
March 11, 2019
Please note that our alternative anonymous ftp access will be
deactivated on or before 31 July 2019 to comply with NASA directives. All data
previously available via ftp can be downloaded via https from the same
locations under the pub
subdirectory on this server.
Four years after the initial loss of communications anomaly with Behind
observatory, NASA has directed to cease periodic recovery operations with the
last support on October 17, 2018. Additional information can be found
October 9, 2018
Both IMPACT and PLASTIC are back to full science operations after the power
spike anomaly on September 23.
October 1, 2018
On September 23, the STEREO Ahead spacecraft detected a power spike on the
electronics shared by the IMPACT and PLASTIC instruments, and autonomously
powered them down. This is believed to be due to a single event upset. A
similar event occured in September 2011. Recovery operations are proceeding.
Most of the IMPACT functionality has been restored, and PLASTIC is expected to
resume operations over the next few days.
June 6, 2018
New labeling has been applied to HI1 and HI2 images to make them easier to read
against a bright background. This also applies to the
pages. In addition, the planet labels have been repositioned so that they do
not overlap with each other.
Decenber 4, 2017
COR1 polarized brightness (pB) images and movies have been added to the
STEREO daily browse
With the aging of the COR1 telescope in the 10+ years since launch, and the
advent of gyroless operations in September 2013, it has become more difficult
to separate the coronal signal from the COR1 instrumental background
immediately after the data are taken. This separation can be more easily
performed in polarized light, which can be derived from most of the COR1 data,
so optional pB images and movies have been added. At the present time, only
the most recent data have been reprocessed to provide pB images.
On Wednesday, November 16, one of the COR1 temperature sensors briefly exceeded
a software limit during a scheduled momentum dump of the STEREO Ahead
spacecraft. This triggered an autonomy rule which disabled the COR1 telescope.
From that point on, until COR1 operations were restored at 20 UT the next day,
the missing scheduled COR1 images disrupted the timing of the image processing
for the other telescopes such that images from one telescope were being
misdirected to the processing for another telescope. This resulted in many
apparent "double exposures", such as
where an EUVI image has been superimposed on a normal HI-1 image. All the
telescopes were affected, except COR1 which was disabled. The temperature
limit on COR1 is being adjusted to keep this from happening again.
October 11, 2016
There have been six attempts to contact the Behind spacecraft using 70 meter
stations between September 27 and October 9 without success. The last
telemetry received from Behind was on September 18, and the last time the
carrier wave was detected was on September 23. Recovery attempts for Behind
have moved back to a monthly schedule until the spacecraft has returned to a
point in its orbit where the attitude is in a favorable configuration for power
October 3, 2016
The following summarizes the activies that have taken place since the last
update on September 19. On September 20, commands were sent for increasing the
battery charge rate to C/4 and closing latch valves. The carrier signal was
very low, intermittent, and carrier lock could not be maintained. After
switching to the +Z LGA, no downlink signal was received. Commands were sent
to the place the TWTA in standby and power on the propulsion tank primary
heaters. No telemetry frames were received. On Friday, September 23, during
the 70m track with DSS-43, the radio science team detected an extremely weak
(~10 dB-Hz SNR) at 2200z for 15 seconds.
The following Tuesday, September 27, during the 2 hour support with DSS-14, no
downlink carrier was detected by the DSN after individually commanding and
loading the test macro to power on the TWTA. The FDF received 17 tracking
points labeled as 2-way. Residuals roamed between -200 and 1054 m/s, with a
few points at similar levels. Mission Operations then directed DSN to begin
configuring for automated battery recovery operations (i.e. repeated multiple
sweeps in a 3 kHz range). At 1455z, automated battery recovery operations
commenced, with MOC repeatedly commanding the following configuration through
EOT - IEM switched power and 1553 off; TWTA to standby, primary and secondary
propulsion tank and -Y panel (R4) heaters on.
BEHIND observatory status: Low main bus voltage, 2 (#6 & 9) out of 11 battery
cells are currently not functioning, high battery temperature, attitude
uncontrolled, rotating at a ~45 second period about its principal axis of
inertia. Current orientation support may support some solar array input; RF
communications on the +Z LGA only supports uplink of short commands to an LGA.
While propellant is suspected to be frozen, from the last telemetry received on
Sep 18th, both propulsion tank latch valves are open, and pressure transducer
#2 is not functioning. Power switching boards are on; nearly all switched
loads off including the IEM (avionics) and PDU 1553 bus with the TWTA in
standby and propulsion primary and secondary tank heaters on and -Y panel (R4)
heaters on. EA mode is enabled. The battery charge rate is C/10. As the
uncontrolled communications link is degrading, necessary macro sequences to
allow the peak power tracker in C&DH standby mode to protect the battery will
be loaded when the communications link supports.
September 19, 2016
On Saturday, September 17, during an uplink array, which consisted of three 34m
stations (DSS-24, 25, & 26) which provided an estimated 10.4 dB gain at the
spacecraft over a standalone 34m uplink at 20 kW, 360 commands were sent for
configuring the spacecraft for a low power mode by powering off excess loads,
powering on all power switching boards, and ensuring the reaction wheels are
powered off in a known configuration. On Sunday, September 18, during a 2nd
uplink array with 70m station DSS-43 monitoring the downlink, during 2 brief
TWTA sampling periods, the carrier signal was received on time with a
continuously fluctuating signal of -170 dBm to -178 dBm with a period of ~45
seconds. Subcarrier lock was intermittent. While the uplink can support short
critical commands, the downlink cannot support telemetry. The radio science
receiver team reported a modulated downlink. As the SNR was not stable long
enough for post-pass telemetry extraction, the LGA was swapped to the -Z LGA to
improve SNR. This improved the carrier level by ~3 dB, with levels of -167 dBm
to -174 dBm. Two telemetry frames were received. While the battery pressure
was good, the temperature needs to be reduced. Daily two hour 70 m supports
have been requested to prevent further battery functional degradation.
September 9, 2016
Today, while the spacecraft was configured for switching to the +Z LGA and
powering on the TWTA before the track this morning, no signal was received
today after repeatedly attempting to power on the TWTA. As the spacecraft
rotation will settle out about its principal axis of inertia which should
continue to provide limited solar array input and communications, battery state
of charge recovery has commenced today. As it appears that the momentum dump
in EA mode was not as effective as we had hoped for during the STEREO BEHIND
recovery into C&DH standby mode late Wednesday, it is suspected that battery
voltage collapsed on Thursday due to sustained high wheel speeds.
BEHIND observatory status: low main bus voltage, 2 (#6 & 9) out of 11 battery
cells are currently not functioning, attitude uncontrolled. Current
orientation supports some solar array input, with possible communications on an
September 8, 2016
Late on Wednesday, September 7, a momentum dump maneuver was carried out on
STEREO Behind. This reduced the spacecraft spin rate from once every two
minutes to once every 38 minutes, approximately. At this lower rate, the star
tracker managed to lock onto a guide star. Telemetry continues to be received.
Mission operations personnel are working on improving the spacecraft attitude
and fully controlling the spin.
September 6, 2016
Over the Labor Day weekend, the mission operations team continued to work on
recovering the Behind spacecraft. The primary emphasis has been on warming up
the propulsion tanks and fuel lines, and on uploading macros in preparation for
an upcoming maneuver to despin the spacecraft and get the solar panels fully
pointed at the Sun again. The power system is stable, and the battery
continues to charge up. Yesterday (September 5) an unexpected feature in the
flight software autonomy rules brought the reaction wheels online for 1.3
hours, perturbing the spacecraft attitude. The wheels have been turned off,
and indications are that the perturbations are damping down again.
September 1, 2016 update
Today, during 4 brief TWTA sampling periods this morning, communications are
still continuous with the carrier signal fluctuating between -158 dBm and -164
dBm. The battery charge rate increased to C/4 for approximately 4 hours during
the track this morning increasing the battery pressure by ~50 psi. An
autonomous momentum dump parameter was loaded, dumped, and verified to EA RAM
and EEPROM and G&C EEPROM. Detailed power subsystem telemetry was received and
cell #6 and #9 (2 out of 11 cells) are indicating 0 volts. Propulsion tanks
are slowly warming and have increased by ~2 deg C. IMU2 was powered on briefly
and initial indications show that it is healthy and was used to confirm the
estimated system momentum level (high). 54 telemetry packets were received.
From the Doppler data analysis by the FDF, the nutation is slowing and
returning to the previous spin axis orientation.
Progress continues on developing the plan and procedure to re-establish
attitude control with very limited battery capacity by conducting an autonomous
momentum dump in EA mode, powering on reaction wheels, and promoting the
observatory to Standby mode.
September 1, 2016
Five telemetry frames were received on Wednesday, August 31. With a good
signal level, -159 to -164 dBm and a ~3 minute period, there was continuous
communications with the TWTA on for 30 minutes. Subsequent analysis showed
that the telemetry from the PDU was stale, so there was no sun vector. From
the one sample, the battery appears to be charging with the TWTA on, with
battery pressures 634 psi and 19 psi, and main bus voltage at 24.9v. As the
uplink was good, the mission operations team began loading uplink time
consuming commands to EEPROM, i.e., autoexec macro 1 and bad gyro data
parameter to EA and G&C. The S/C emergency was reinstated (had ended at
midnight) and a 6.2 hour DSS-14 support was added starting at 1815z. As the
signal had sufficient margin, the downlink rate was increased to 35 bps, which
provides one (1 packet/frame) every 102 seconds. Eight good telemetry frames
were received, including 3 memory dump packets and one temperature packet.
Unnecessary systems that were found to be on were turned off to decrease the
load on the battery. The 3 loads to EEPROM were verified from dumps
August 31, 2016
On Tuesday, Aug 30, the DSN once again detected the downlink carrier signal at
1321z from STEREO BEHIND. The signal was intermittent with a peak level of
-159 dBm. FDF analysis of the Doppler residuals shows the signal fluctuating
at ~140 seconds and a spin-axis to Earth angle of ~36 degrees. Note that the
TWTA was only on for 30 minutes to conserve battery state of charge. A more
stable uplink is required to load parameters necessary for conducting an
autonomous momentum dump to re-establish attitude control. From Friday's IEM
power on, four additional telemetry packets were processed (one was a
duplicate) and will be distributed. The reaction wheel latching relays were
commanded off along with all unnecessary power loads.
August 30, 2016 update
The DSN detected the carrier signal again from STEREO Behind on the morning of
Tuesday, August 30. More details to follow.
August 30, 2016
The DSN has been able to extract 5 additional telemetry frames from Friday's
IEM power on. These frames are being processed and the telemetry from the 5
critical packets will be distributed. An updated recovery plan was developed
and discussed during the daily telecon. On Tuesday, carrier recovery will be
commanded, attempting to power on the TWTA. If the downlink signal is
detected, the TWTA on time will be limited to ~21 minutes, which is 1.5 times
the period of the beat frequency of rotation and nutation. The reaction wheel
latching relays will be commanded off. If no signal is detected, the battery
recovery commands will be sent for the remainder of the support and the next
day’s support will be shortened to 4 hours. This operational cadence will
continue until BEHIND is restored to active attitude control or the DSS-63 time
ends on Sep 11th.
BEHIND observatory status: Unknown state of power, uncontrolled attitude,
complex rotation (~14 minute rotation with the previous ~2 minute rotation)
about the principal axis of inertia. Current orientation may support
communication near the edge of the + Z LGA with some solar array input.
Propulsion tanks are frozen.
August 28, 2016 update
Today, the DSN created a new acquisition sequence for only sweeping a 3 kHz
range about the best lock frequency. This was used successfully during the
morning Goldstone support to repeatedly sweep and send battery recovery
commands. It was agreed to continue battery recovery tonight and on a 4 hour
support on Monday. The carrier recovery is scheduled for Tuesday during a 4
hour support with radio science receivers recording.
BEHIND observatory status Unknown state of power, uncontrolled attitude,
complex rotation (~14 minute rotation with the previous ~2 minute rotation)
about the principal axis of inertia. Current orientation may support
communication near the edge of the + Z LGA with some solar array input.
Propulsion tanks are frozen.
August 28, 2016
On Saturday, August 27, during the evening recovery track, no downlink signal
was received after repeated commanding the transmitter on. Battery recovery
commands were sent for the last hour of the support.
On Friday evening, as battery voltage was decreasing from the three telemetry
packets received, the transmitter was powered off early. However, the downlink
signal was lost 6 minutes earlier than expected. It is speculated that with
the complex roll, which resulted from powering on the IEM, the battery voltage
may have collapsed at some point.
BEHIND observatory status Unknown state of power, uncontrolled attitude,
complex rotation (~14 minute rotation with the previous ~2 minute rotation)
about the principal axis of inertia. Current orientation may support
communication near the edge of the + Z LGA with some solar array input.
Propulsion tanks are frozen.
August 27, 2016
The primary propulsion tank heaters (~30W) were enabled at 1530z on Friday, Aug
26. During the second track, after the IEM was powered, the downlink signal
would drop out periodically. From analysis of the Doppler residual data from
the FDF, the rotation is more complex, there is an ~14 minute rotation with the
previous ~2 minute rotation. This appears to have shifted the spin axis from
10.5 deg to 22 deg. Three packets of critical telemetry were received. From
this very limited data, as expected, the observatory is quite cold, with the
battery at 30% state of charge and generating power to support ~150W. From the
propulsion tank pressures, the tanks appear to be frozen; however, no
temperature data were received. The Sun angle averaged ~ 60 degrees. As the
main bus voltage was 24v and falling, the transmitter was powered off early.
While early in recovery, 2 of 11 battery cells appear not to be functioning.
Verified that the increased battery charge rate command to C/4 was received.
From engineering team discussions, it was decided to power off the IEM and
power on the secondary battery heater to allow the battery to recharge. The
secondary propulsion tank heaters were also powered on to continue thawing of
BEHIND observatory status: Avionics off, uncontrolled attitude, complex
rotation about the principal axis of inertia. Current orientation supports
nearly continuous communication near the edge of the + Z LGA with some solar
array input. Propulsion tanks are frozen. Secondary battery and propulsion
tank heaters are on in between DSN tracks.
August 26, 2016
Based on recent thermal analysis, the propulsion tanks will take from 65 to 308
hours, depending upon current temperature and how many heaters circuits can be
used, to warm the hydrazine in the tanks to 2 deg C. As power is available
now, the secondary propulsion tank heaters (~30W) have been enabled. Also,
selected power switching boards were powered off to prevent unwanted loading in
preparations for powering on the avionics. To allow for sufficient time for
procedure testing and review, the powering on of the avionics has been moved to
the second track on Friday.
BEHIND observatory status: Avionics off, uncontrolled attitude, rotating about
the principal axis of inertia. Current orientation supports continuous
communication near the edge of the + Z LGA with some solar array input. No
telemetry has been received and therefore detailed status is still unknown.
Secondary propulsion tank heaters are on in between DSN tracks.
August 25, 2016
The spin axis is estimated to be 12 to 14 degrees from the Earth-Sun line to
spacecraft. Due to the 22 degree/year mean drift rate, the current geometry
which provides solar input and continuous RF communications will not occur
again till 2022. A separate analysis using the Doppler shift data was
conducted by the RF lead and the FDF which was in close agreement with the G&C
observations. It was concluded that the solar arrays are generating ~250W and
loading during recovery must stay below this to prevent battery collapse. The
draft plan for powering on the avionics (IEM) and G&C recovery was reviewed.
Command procedures and testing on the hardware simulator are in progress.
August 24, 2016
Correction: the principal axis of inertia, for which BEHIND is most likely
rotating about, is located in the X-Y plane inclined about 60 deg away from the
+X axis toward the -Y axis. A draft plan for powering on the avionics (IEM)
and G&C recovery will be sent soon for review.
August 23, 2016
After reviewing the downlink signal levels, it was concluded that STEREO Behind
is most likely rotating about its principal axis of inertia, located in the X-Y
plane inclined about 30 deg away from the +X axis. While this uncontrolled
orientation appears to be power positive now, it will drift off, and the
estimate is that it may not return until next summer. The ~2 minute
rotation/wobble is ~3 deg/sec which is beyond what the momentum wheels can
handle. This means that any attempt to despin the spacecraft at the present
time would result in saturation and subsequent autonomous momentum dump, for
which the spacecraft has not yet been prepared.
The FDF will generate a new orbit when sufficient data is available. For
subsequent tracks, will go two-way as soon as possible to collect more coherent
August 22, 2016
On Sunday, August 21, contact was reestablished with the STEREO Behind
spacecraft for the first time in 22 months, since contact was lost on October
1, 2014. See
this news release for more information.
During the monthly recovery operations, the Deep Space Network station DSS-14
established lock on the STEREO Behind downlink carrier at 2227z on Sunday, Aug
21st. The two-way downlink signal was -168 to -178 dBm, over what appears to
be a ~2 minute rotation. The Doppler residual frequency was in the predicted
range. The DSN locked to the 25 kHz emergency subcarrier frequency indicating
that the observatory was transmitting on the low gain antenna as expected. The
DSN radio science receivers were recording and the team confirmed the spectrum
of the carrier, the residual frequency, and the subcarrier. The downlink was
received for 2.4 hours through end of track.
NASA project management has reinstated the spacecraft emergency for STEREO
Behind. A 3 hour support with DSS-43 commenced later with an improved one way
signal of -158 to -168 dBm. The best lock frequency range was determined and
the transmitter high voltage was powered down, on the A side on the first
command sent, to save battery power.
No telemetry was received as expected since the avionics were purposely powered
off to maintain battery state of charge. While quite early, recovery is
expected to proceed slowly to preserve a positive power balance, assess
observatory health, re-establish attitude control, and warm all subsystems and
November 17, 2015
The STEREO Ahead observatory has returned to full operations on the main lobe
of the high gain antenna. The low rate data stored on the recorder since the
start of side lobe operations has been read out, and the recorder has been
restored to its original configuration. All the instruments have resumed
normal operations. The IMPACT SWEA and STE detectors will be powered on and
brought back up to full operations over the next few days.
November 9, 2015
The STEREO Ahead observatory has returned to using the main lobe of the high
gain antenna. From this point on, space weather beacon data will be available
again from the NOAA antenna partners between DSN tracks. The mission
operations team will now start to download the low rate data that was stored on
the recorder since the start of side-lobe operations on August 20, 2014. Once
this is completed, the recorder will be reconfigured, and the instruments will
be returned to their prime science mode. In the meantime, the instruments will
continue to produce telemetry at the side-lobe rates for the next few days.
See the planning page for more details about the
July 16, 2015
The spacecraft guidance-and-control system was returned to normal operations
when reaction wheel #3 was power cycled and resumed responding to torque
July 15, 2015
The IMPACT team reports that all of their instruments are now working and
producing science data, with the exception of SWEA and STE which won't be
turned on until the spacecraft returns to the main lobe of the high gain
antenna in November. Because of the current difficulties with commanding due
to solar scintillation effects at such a small separation angle from the Sun,
the SIT instrument is using the original table set that the instrument was
launched with. This table set is known to have some calibration problems, but
this is considered to be better than having no data at all. He intensities are
about a factor of five too low, while the H, O, and Fe intensities are
approximately correct (within a factor of two). The IMPACT team plans to
upload the most current table set when the command link is more stable, which
is expected to be in several week's time.
July 14, 2015
JPEG images from the SECCHI EUVI and HI2 telescopes are now appearing on the
SSC website. Images from the other telescopes will be made available as soon
as enough data have been collected to derive instrumental backgrounds. The
SECCHI team is also working through the issue of updating the pointing
information in the images to take into account the changed attitude of the
spacecraft after solar conjunction. The headers in the COR1 and COR2 FITS
files have been corrected, and work is proceeding on the other telescopes.
Incorrect EUVI pointing information is currently interfering with the
production of heliographic maps. It is expected that this will be corrected
The IMPACT team reports that MAG, SEP, and HET are producing science. Regular
science data from SIT-A from July 13 after the HV was ramped up showed that the
instrument MCPs were triggering normally, and events were being analyzed.
However, the on-board rate computation was returning 0 counts in all boxes, due
to the dropouts in the table loads experienced on July 13. Given the current
issues with dropped commands due to solar interference, it was decided to
reboot SIT-A, since this loads the original table set from SEP central. This
table is not optimally calibrated, but approximately calibrated data is better
than no data at all. The team's plan is to upload the up-to-date table set
when the STEREO commanding link is more robust, perhaps on August 1st, when the
SPE angle is at 3.0 degrees.
The PLASTIC MCPs have been brought up to 2590V, which was the original
operating voltage at the beginning of the mission. The PAC was brought to
-18kV, monitored for stability, and then brought to the full mission operating
value of -20kV. The instrument was then put into mode 3 to collect monitor
rates. The entrance system is not yet enabled.
July 13, 2015
On Saturday, Jul 11, the SECCHI instrument was powered back on. The team
verified with the EUVI telescope that the spacecraft was correctly pointed, and
re-opened the COR1 and COR2 doors. All the telescopes are operating normally,
but some ground software issues are currently interfering with the production
of JPEG images for the SSC website. The IMPACT team reports that HET is now
producing science. Due to solar interference, efforts to patch LET have been
slowed. The SIT-A high voltage ramp-up was completed today, and the analog HK
values from the instrument are at nominal levels. The largest of the lookup
SIT tables has not been successfully reloaded, apparently due to ground GSE
problems, but the smaller SIT tables have now been loaded. PLASTIC continues
to ramp up their high voltages.
July 10, 2015
The IMPACT team reports that MAG and SEPT are producing science. Due to
communication interference, efforts to patch LET have been slowed and will
continue on Monday. HET is producing some science, but a table load needs to be
completed on Monday to get back to its nominal state. SIT has a bit more
configuration to do as well plus its high voltage needs to ramp up so it will
be sometime next week before it is producing science. All these instruments
appear to be healthy. No anomalous behavior has been seen after the long
July 9, 2015
Post-solar-conjunction instrument recovery continued with the powering on of
the IMPACT and PLASTIC instruments. The IMPACT MAG, SIT, HET, LET and SEPT
subsystems have been powered on. SWEA and STE will remain off until the
spacecraft returns to the main lobe of the high gain antenna later this year.
MAG has already started producing science data. The SEP suite
is expected to be in science mode sometime on July 10, except for SIT which
will take several more days to bring back to full operating mode.
July 8, 2015
The STEREO Ahead spacecraft was returned to three-axis stabilized mode today,
and the operations team has started the process of returning the spacecraft to
normal operations. The scientific instruments are expected to be turned on
over the next few days. The S/WAVES radio instrument has remained on all
throughout the superior solar conjunction period, and has started to return
data again. More information on the status of STEREO Ahead will be
provided as it becomes available.
June 4, 2015
A simulation of one possible model of the events that led up to the loss of
contact with STEREO Behind is available here.
March 24, 2015
The STEREO Ahead was reset into its "safe mode"
16:00 UT on 24 March 2015 in preparation for superior solar conjunction.
Normal operations are expected to resume in July 2015. Please see
this link for more
March 20, 2015
The IMPACT, PLASTIC, and SECCHI instruments on STEREO Ahead were turned off at
16:00 UT on 20 March 2015 in preparation for superior solar conjunction. They
are expected to resume operation in July 2015.
A new web page has been put together describing the recent
loss of contact with the STEREO Behind
October 7, 2014
Communications with the STEREO Behind spacecraft were interrupted on October 1,
immediately after a planned reset of the spacecraft performed as part of a test
of solar conjunction operations. The cause of the anomaly is not yet known,
though a sensor anomaly in the guidance and control system is suspected.
Attempts to recover the spacecraft are continuing.
September 3, 2014
A massive proton storm caused by a large flare on the far side of the Sun hit
both STEREO spacecraft starting September 1, 2014. The high energy particle
fluxes were so high that the star tracker reset on both spacecraft reset within
minutes of each other. The star tracker on Behind returned to full operation
after 4.7 hours, and on Ahead after 18.7 hours. Both star trackers are now
The storm was so massive that many of the SECCHI images during the storm do
not pass their quality check, and therefore do not appear on the daily browse
pages. Other images from the storm period that do make it onto the web pages
are heavily contaminated by the proton storm, and are highly distorted. This
is particularly true for the HI-1 and HI-2 images taken during the height of
August 20, 2014
A new procedure has been developed for processing HI-2 images during side lobe
operations. The old procedure depended on having pairs of images 2 hours
apart, in a process known as "running difference". This worked fine when we
were getting 24 hour coverage. However, now that the Ahead spacecraft is
operating on one of the side lobes of the high gain antenna, we only get a few
hours of real-time data per day, during the periods when the spacecraft is in
contact with one of the 70 meter ground stations. With such restricted
telemetry, only a small number of HI-2 images has a preceeding image to form
the running difference. The new technique uses nearby images to generate a
background image for subtraction, and allows all the images to be
processed. Experimentation shows that coronal mass ejections still show up in
these images, though not quite as clearly as in the running difference
technique. Behind data will continue to be processed as running differences
until that spacecraft also starts using the antenna side lobe at the end of
November. For more information about the STEREO side lobe operations, please
August 20, 2014
The first telemetry downlink from the STEREO Ahead spacecraft during the
side-lobe operations period has been carried out successfully. Beacon data was
collected from all the instruments, and processed for the real-time image and
plots pages. There are some minor issues which have been identified in the
ground processing of the SECCHI images in this new mode of operations, but
they should be corrected soon. The spacecraft performed as expected. For more
information about the STEREO side lobe operations, please see this
August 19, 2014
The STEREO Ahead spacecraft has been reconfigured for side lobe operations.
The solid state recorder has been played back, and repartitioned to store
spacecraft housekeeping and in situ beacon telemetry for eventual
playback once normal operations are resumed in January 2016. The high gain
antenna has been moved to the first side lobe position; the first pass using
this configuration will be on Wednesday, August 20. See this
important notice for more information.
August 15, 2014
The change in COR1 processing implemented on August 14 did not work out as
expected, and the software has been returned to its previous behavior.
However, the initial backgrounds for the most recent COR1-Ahead data have been
August 14, 2014
Because of the difficulty in deriving good instrumental backgrounds at this
stage of the mission, the strategy for generating the browse images for the
COR1 telescopes has changed. In the old procedure, regions where the
instrumental background was overestimated would end up completely dark. The
new procedure should correct this problem, but with the side affect that some
areas in the outer corona may now appear too bright. However, it was felt that
this was preferable to completely losing visibility in parts of the image.
It's anticipated that after sufficient time has elapsed to provide better
backgrounds, and the images have been regenerated, the difference between the
two methods will be minimal.
July 11, 2014
The test of operating the STEREO Ahead spacecraft during the upcoming period of
reduced operations has been successfully
concluded. Recovery of the science instruments after being off for the last
several days has begun.
June 26, 2014
Unexpectedly high temperatures in the high gain antenna feed horns on both
STEREO spacecraft will require corrective action in the coming months that will
severely limit science operations. The high temperatures are being caused by
the small angle between Earth and the Sun as seen from each spacecraft. In
other words, pointing the antenna at Earth is putting too much solar heat on
the antenna feed horn. To bring down the feed horn temperature, and preserve
the spacecraft for years to come, the antennas will be pointed off at an angle
from both Earth and the Sun, so that less heat will fall on the feed horns.
Communication will still be possible using one of the antenna side lobes, but
the telemetry rate will be extremely low. What instrument operations
can be supported while the antennas are off-pointed is still being studied.
A test of operating the STEREO Ahead spacecraft in this antenna off-pointed
mode will be conducted during the week of July 6-12, 2014. All science
instruments will be turned off during this time, and instrument recovery
operations are expected to take several days.
More information about the upcoming period of reduced operations can be found
on this page, which will be updated as
more information becomes available.
May 30, 2014
A new version of the SECCHI/HI Level-2 product is
available on the STEREO Science
Center website. These data have have actually been partially available for a
while now, but announcement was delayed until the ingestion of the files was
mostly complete. At the time of this writing, some data from the first year of
the mission is still being ingested, but the data should be complete from 2008
The new data are available in three different units: detector data numbers per
pixel per second (DN/Pixel/Sec), Mean Solar Brightness (MSB), and the
astronomical diffuse magnitude scale known as S10. The MSB and S10 data have
had the diffuse brightness correction applied. The
file naming convention has been updated
for these data.
January 6, 2014
The Inertial Measurement Unit (IMU) on STEREO Behind failed at 9:46 UT on
Sunday, January 5, putting the spacecraft into coarse point mode. Recovery
operations are currently being carried out. All the instruments continue to
take data. However, the COR1 and COR2 doors are closed.
Update: Fine pointing mode has been restored on STEREO Behind. The COR1
and COR2 doors have been reopened.
The STEREO Behind spacecraft has been completely recovered, and is operating
nominally. The cause of last week's transponder anomaly is still under
July 19, 2013
The STEREO Behind spacecraft is currently in a low-rate telemetry mode. The
mission operations team is diagnosing the problem. More information will be
posted as it becomes available.
Update:The The transponder on the STEREO Behind spacecraft has been
recovered back into 120 kbps mode. The remaining recovery activities,
including activating the beacon rate between passes, will be completed on the
next pass. The rest of the spacecraft has been operating normally the entire
time, and the instruments have been collecting data.
February 14, 2013
A new web page has been put together describing the possible observations of
Comet ISON by STEREO
in October-December 2013.
December 4, 2012
The mode of operations for the COR1 telescope on STEREO Behind was changed back
to the normal sequence of 0, 120, and 240 degrees.
November 29, 2012
Starting November 29, the mode of operations on the COR1 telescope on STEREO
Behind was changed to take images at polarizer angles of 60, 180, and 300
degrees instead of the previous 0, 120, and 240 degrees. This was done in an
attempt to correct occasional position errors that had developed in the 240
degree images. Changing the polarizer angles introduces subtle effects in the
instrumental background. It will take some time for sufficient data to be
collected to create new background files. In the meantime, provisional
background files have been formed based on the older data. As a result, the
COR1-B images will appear noisier than usual until new background files are
November 27, 2012
Users may have noticed that there have recently been a significantly smaller
number of SECCHI images from the Behind spacecraft, and large gaps in the
IMPACT, PLASTIC, and SWAVES data from Behind. This is due to a shortage of
telemetry coverage caused by Deep Space Network schedule conflicts with other
missions. This situation started in mid-November 2012, and is expected to
continue for the next several months. In upcoming weeks, the Ahead spacecraft
will also start to be affected.
The daily STEREO
pages now include daily synoptic maps generated from a combination of STEREO
and SDO images, in all four EUVI wavelengths. These daily maps have been
generated back through 2010, and earlier dates will be available soon.
March 26, 2012
searchable STEREO publication database is now available. This replaces the
old database system which had to be taken offline. Authors of STEREO-related
articles in the refereed literature are encouraged to submit them for inclusion
in the database once they are accepted for publication. It would be
particularly helpful to include the DOI, volume, and page number.
December 14, 2011
A new running difference browse product is now available for the SECCHI EUVI,
COR1, and COR2 telescopes. These running difference images are available on
the individual daily browse pages, and on
the latest images page, and should be
available soon via the image search tool.
Currently, running difference images are available only for dates starting
November 1, 2011, but earlier dates will be filled in over time.
July 22, 2011
The power outage earlier reported on the home page for July 22-23 has been
July 20, 2011
The software used to generate the SECCHI browse images has been changed to more
closely reflect the actual data. In the previous version of the software, when
the JPEG images being generated were larger than the original images, the data
were interpolated to the larger size. The new version of the software resizes
the images without interpolation. The result is a less-smooth, more
"pixelated" image, but which is more representative of the actual data.
Particularly affected are the beacon images. The smoother beacon images
produced by the previous version sometimes confused people into thinking that
they saw structures which were not supported by the actual data.
May 18, 2011
The SECCHI EUVI, COR1, and COR2 telescopes on STEREO Behind picked up an
interference pattern on 9 May 2011 around 17:20 UT, thought to be due to a
single event upset to the Camera Electronics Box (CEB). The CEB was restarted
to fix the problem on 12 May 2011; however, in the meantime the background
images for COR1 and COR2 had become corrupted, preventing the team from
immediately realizing that the problem had been solved. New backgrounds are
now being produced, and the browse images are being
regenerated as corrected backgrounds become available.
April 5, 2011
A new "Downlink Performance" data product is now available as part of the
Ancillary Data set.
January 13, 2011
The IMPACT/PLASTIC Data Processing Unit on Behind was autonomous switched
off on 8 January 2011 due to unexpectedly high current. The IMPACT and
PLASTIC instruments were switched back on, and all the instruments are now back
into normal operating mode.
December 17, 2010
The SECCHI team is now making available movies made up from the last seven days
of data. These movies are available from their
page, under the sidebar heading "Current Weekly Movies". Note that each STEREO
spacecraft is now within the field of view of the COR2 telescope on the other
December 16, 2010
The PLASTIC team has instituted a new data browse product called "Protons
Projected to Earth" on their
page. These overplot the STEREO A, B and Wind proton data sets, with a simple
time translation assumed for A and B. The purpose is to demonstrate how
STEREO-B data can be used as an advance proxy for L1.
December 1, 2010
The remaining problems with connectivity between the STEREO Science Center and
the Mission Operations Center after the move on November 29 have been resolved.
All SSC services should now be functioning normally.
November 30, 2010
The STEREO Science Center has been successfully moved to its new location, and
the website and beacon services are back up and running.
We are now making available a prediction of the
state of the Sun during the upcoming total solar eclipse on 11 July 2010, based
on what STEREO Behind saw at the same heliographic longitude on 6 July 2010.
The problem with accessing recent AIA data for the STEREO
synoptic maps has been resolved.
July 7, 2010
We are currently having problems accessing recent AIA data for the STEREO
synoptic maps. The VSO and AIA teams are working on the problem, and we hope
to have it resolved as soon as possible.
SDO/AIA images are now being used to supply the "Earth-view" in the STEREO
Latest Images and
Daily Browse Images pages for dates after April 16,
2010. SOHO/EIT images are used for earlier dates, or if the SDO/AIA data are
unavailable. Since AIA does not observe the Fe XV line at 284 Angstroms, the
similar Fe XIV image at 211 Angstroms is used instead. Note that the SDO/AIA
team has chosen to display their images in different color tables than were
used for the SOHO and STEREO projects.
June 22, 2010
The STEREO heliographic maps on our
Images page now include SDO/AIA data for the Earthward-facing part of the
Sun. Once the two STEREO spacecraft reach 180 degree separation on 6 February
2011, the combination of images from all three spacecraft will give us a
complete view of the entire Sun.
Level-2 archive has been reorganized. The former contents have been
moved to a new subdirectory called
and new subdirectories
have been added.
January 1, 2010
The pages on image artifacts due to
beacon processing and
cosmic rays have been updated to show how these two
artefact sources interact.
November 18, 2009
A new webpage has been inaugurated showing side-by-side
comparisons between the latest
SECCHI beacon images, and the most recent GONG far-side maps. When candidate
magnetic regions appear in the GONG maps, one can look for enhanced brightness
in the corresponding area in the EUVI maps. There is still a region on the far
side of Sun which is not yet observed by STEREO, but this region will shrink
over time, and we should be able to observe the entire Sun by February 2011.
November 3, 2009
Beacon telemetry files are now
on the website for instrument teams who want to use the beacon telemetry to
fill gaps in the level 0 telemetry
November 2, 2009
The IMPACT team has removed the following directories from their Level 1 data
and the same for behind. MAG data are now to be found in the RTN and SC
directories for data in RTN and spacecraft coordinates respectively.
October 15, 2009
We have been receiving a number of questions recently about planets visible in
the STEREO telescopes. A new
STEREO Planet Finder page shows the calculated
positions of planets in the latest SECCHI beacon images. One can also use the
STEREO Orbit Tool for older data. Select either the
inner or outer solar system options to see which planets might be in the field
of view of the STEREO telescopes.
August 26, 2009
The SECCHI instrument team has instituted new software for their HI2 beacon
images. These images are now available on the
latest images and daily
browse pages. To save telemetry, only the sunward half
of the images are sent down in the low rate beacon telemetry stream.
IMPACT/PLASTIC Level-3 event lists from UCLA are now
archived within the SSC.
August 6, 2009
The IMPACT/SIT instrument has now been restored to full operation. Now all the
STEREO instruments are recovered from the system reset on August 4.
August 5, 2009
The IMPACT/SWEA high voltage on Ahead is now at its nominal value. The only
remaining detector still needing to be fully recovered is IMPACT/SIT.
August 5, 2009
PLASTIC on Ahead is back to operating mode. The high voltage supplies are
still warming up, and are expected to take several hours to reach equilibrium
temperatures. This may affect the data values during those hours.
August 4, 2009
The SECCHI telescope suite has been recovered, and is taking images again.
August 4, 2009
All the instruments have been powered back on successfully. Some beacon
telemetry is now available from IMPACT and SWAVES. Instrument recovery will
continue over the next few days.
August 4, 2009
Powering up of the instruments has begun.
August 4, 2009
The STEREO Ahead spacecraft was successfully reset today (Aug 4) to load new
guidance and control software. The spacecraft is back on the high gain
antenna, and recovery is proceeding as scheduled. Powering up of the
instruments is expected to begin soon.
August 3, 2009
The STEREO Ahead spacecraft will be reset on August 4. Complete recovery is
expected to take several days. This page, and our
status page will be updated as more information
becomes available. The expected sequence of events is as follows:
The instrument start preparations for shutdown at 5:45 UT. High voltages
will be ramped down.
Instruments will be powered down at 9:40 UT.
The spacecraft will be commanded to reset around 10:30 UT.
Powering up of the instruments is expected to commence around 15:50 UT.
Pass ends at 17:40 UT.
Instrument recovery will continue over the next couple of days.
July 28, 2009
PLASTIC Level-2 data are now available in
July 23, 2009
The PLASTIC Level-2 directories have been reorganized. Under the directories
for each spacecraft now appear directories labeled "10min", "1hr", and "1min"
for different time resolutions. The previous data appear in the "1min"
July 15, 2009
The STEREO website has been restored. There are still a few features which are
disabled, but most things should work. In particular, the popular
image search utility is working again, as is the
orbit tool. We are endeavoring to restore the remaining
features as quickly as possible.
July 14, 2009
The STEREO/VSO interface, which went offline along with the webserver on June
22, is back online. STEREO data can now once again be retrieved either
through the web interface,
or through the IDL interface (recommended), such as through the routine
July 13, 2009
Time-elongation plots of SECCHI beacon
data are now available. These plots are designed to show the propagation of
CMEs through the telescope fields of view.
July 2, 2009
The data and browse directories have been restored to the website, but scripts
are still not functional.
June 29, 2009
The STEREO Science Center website went offline on June 22, 2009. Currently,
we're running a minimal website with some, but not all, of the functionality of
the original website. Please excuse us while we try to address the problem.
May 18, 2009
We have been informed that all instruments have now been completely recovered
from the planned spacecraft reset on May 12, 2009, including ramping up high
May 14, 2009
The STEREO Behind spacecraft was successfully rebooted on May 12, 2009 to use
the new Guidance and Control software. Recovery of the spacecraft has been
completed, and all instruments have been powered up and are operating. High
voltages on some of the instruments may still require adjustment.
May 12, 2009
Starting around 23:00 UT on May 12, 2009, the STEREO Behind spacecraft will
be reset to load a new Guidance and Control software version. Full recovery of
all the instruments is expected to take several days. Please check the
status page for updated information as it becomes
May 11, 2009
Initial processing of COR1 images was changed in an attempt to bring out more
of the solar features before the preliminary time-dependent background
subtraction has settled down to its permanent value. Later processing of the
COR1 images, at 15 and 35 days after the observation date, uses the original
This new procedure turned out to be unsuccessful, and was
May 4, 2009
The PLASTIC team now provides solar wind proton data as "condegrams", showing
five Carrington rotations at a time in a spiral format. This brings out
recurrent features (such as CIRs), and shows changes in magnitude from one
Carrington rotation to the next. These plots are available from our
instrument data page.
April 8, 2009
The SSC is now providing heliographic maps formed from the latest SECCHI Ahead
and Behind EUVI images to provide a more integrated view of the current state
of the Sun. The synoptic map, updated hourly, can be found on our
latest images page.
Note just how much of the Sun we can see now.
The IMPACT SEPT files have been reprocessed to remove the timestamp bug. The
corrected files are version V06 and above. SEPT files below version V06 should
not be used.
February 25, 2009
Updated Warning: A software bug has been discovered causing times in the
IMPACT SEPT Level 1 data to be too early by about 33 seconds. The IMPACT team
is in the process of correcting the files and appreciates your patience. They
have verified that the problem exists only for the IMPACT SEPT
level 1 data. No other IMPACT data products, including products for MAG, SWEA,
STE, LET, SIT and Beacon, are affected.
February 24, 2009
Warning: A software bug has been discovered causing times in the IMPACT
CDF files to be too early by about 33 seconds. The IMPACT team is in the
process of correcting the files and appreciates your patience. They have
verified the problem exists for the IMPACT SEPT and Beacon data files and may
also be present for several other IMPACT Level 1 data products. The times are
known to be correct for the LET Level 1 data product.
September 11, 2008
Although some technical problems may still need to be worked out, data
ingestion from NRL has resumed. The most recent data has been ingested, but
some backlogged data is still being copied over.
September 5, 2008
Because of server problems at NRL, the processing and ingestion of SECCHI FITS
data is temporarily suspended.
August 22, 2008
A new IMPACT/PLASTIC Level 1 data product including data from the 200h
housekeeping packets is now available on the SSC server for both
August 15, 2008
Ingest of SECCHI data into the Stereo Science Center was resumed on Tuesday,
August 12. The backlog of data has now all been ingested and processed into
August 8, 2008
Ingest of SECCHI data into the Stereo Science Center has been temporarily
suspended until additional disk space can be installed. Data ingestion is
expected to resume on Tuesday, August 12th, 2008. All other data products
continue to be ingested.
July 31, 2008
The first announcement
for the combined STEREO-3/SOHO-22 Workshop, "Three eyes on the Sun -
Multi-spacecraft studies of the corona and impacts on the heliosphere", is
The STEREO proposal to the 2008 Senior Review is now available from our
April 8, 2008
The PLASTIC level-1 data archived at the SSC have been moved down into a new
level1 subdirectory to make way
for new level-2 data which are now
March 20, 2008
Daily browse movies are now available from the
Data Center. This website allows one to examine side-by-side images from
STEREO Ahead and Behind, or from two SECCHI telescopes on the same spacecraft.
December 27, 2007
Normal operations have resumed on Behind, one day earlier than originally
expected. Both spacecraft are now operating as expected.
December 26, 2007
The Behind star tracker has continued to perform nominally since December
23. Should no further problems develop, Mission Operations plans to resume
normal operations on Friday's track (Dec 28).
December 23, 2007
The Mission Operations team was able today to command the star tracker on
Behind back into operational mode. The star tracker continued to operate
throughout the track. As a precaution, use of the star tracker was suspended
at the end of the track, and the spacecraft was switched from the high gain
to low gain antenna. Mission Operations will continue to staff tracks, and
proceed with caution regarding ST usage. Contingency planning will continue
as will discussion with the star tracker supplier.
December 22, 2007
Problems persist with the star tracker on Behind. The high gain antenna
continues to point to Earth, and the Mission Operations team was able to use
it to download science telemetry. All other spacecraft systems continue to
December 21, 2007
The star tracker on STEREO Behind had an anomaly at 10:10 GMT this morning.
This resulted in the spacecraft autonomously switching to the low gain
antenna. All other spacecraft systems are healthy. Diagnostic telemetry is
being collected, and corrective action is under consideration.
Science data is still being collected, but at the current low telemetry rate
it is not possible to send it to the ground. Some science data may be lost
when the onboard recorders reach their maximum capacity.
December 19, 2007
Running difference images and movies from the SECCHI Heliospheric Imager
HI-2 telescope are now available on the SSC browse and
image search pages. So far, only a few days
are available, mostly in December 2007, but more days will be populated in
the near future.
Unlike the other SECCHI telescopes, the HI-2 images are only processed from
the full resolution level-0 science data. Thus, there is a delay of several
days before any HI-2 images are available.
December 6, 2007
Data from the IMPACT STE detectors are now available on the
Daily MPEG summary movies are now available from the
Daily Browse page.
August 10, 2007
Images from the SECCHI HI1 telescope are now available on the
Daily Browse and Image Search
Tool pages. Because the HI1 images are derived from the level-0 science
data, they take a few days to appear on the website.
Several improvements have been made to the in-situ beacon pages at
The IMPACT magnetometer data is now in the standard Radial-Tangential-Normal
(RTN) coordinates, and total magnetic field strength has been added to the
plots. New pages have been added for solar energetic particle data.
March 22, 2007
The daily data browse pages are now available at
So far, only a few days worth of data are available, but earlier data will be
steadily added. We're also working on adding more in-situ data, as well as the
daily summary plots from SWAVES.
New web page for auxiliary data, which is
data produced by other observatories either in conjunction with the STEREO
project, or which is useful for analyzing STEREO data.
January 23, 2007
The Behind spacecraft flew by the Moon for the second
and last time on January 21. Both spacecraft are now in heading away from
Earth into their orbits around the Sun. The official science mission started
The baffle cover on the SECCHI Heliospheric Imager on Behind was opened on
January 11. The scientists were thrilled to find that Comet McNaught was in
the HI-1B field of view. The IMPACT SIT and SEPT covers were opened on Behind
on January 16. All instrument covers are now open.
December 22, 2006:
The A spacecraft performed its lunar flyby last
Friday and is now in heliocentric orbit.Â The drift rate of the spacecraft is
+21.66 degrees/year (relative to the earth), this is well within its
specification of 22+/- 2 deg/year. The B spacecraft also performed a lunar
flyby, but its trajectory has another flyby scheduled for 21 January 2007.Â The
B spacecraft successfully completed its final trajectory adjustment maneuver on
December 14, 2006:
All the subsystems on both spacecraft continue to
perform very well.Â On Monday, Dec. 11, the Ops team performed a peak power
test on the A-spacecraft.Â The arrays are producing slightly more power than
expectedÂ (720W vs 690W).Â The G&C team has started to tweak the control
algorithms with the result that mechanical oscillation of the SWAVES antennae
has completely disappeared on both spacecraft.Â They will continue to fine tune
the system and are planning a test which would run all the wheels through all
speeds to investigate the effect of wheel speed on jitter.
The SECCHI SCIP-B telescope doors (EUVI, COR1 and COR2) were successfully
opened Dec. 13 at 6:30am. First light images were taken and reviewed by a bunch
of very happy scientists on the east and west coasts. Â Performance was as
expected and comparable to the SCIP-A telescope images taken last week. In
addition, there was a successful opening of the first HI telescope door on
S/C-A. The HI images appear to be exceptional. This means that of the 10
SECCHI telescopes, 8 have successfully opened their doors and taken good
images. The HI-B door, which covers the last 2 telescopes, will open at the end
of December or early January, depending on when we verify that there will be no
more B Observatory maneuvers.
The IMPACT SEPT-NS, SEPT-E and SIT doors were deployed Dec. 14 on Ahead. In
anticipation of this exciting event, the Sun decided to become active making it
easy to confirm the door openings in the science telemetry. There were 5 door
actuations - one for SIT and two for each set of doors on SEPT-E and SEPT-NS.
The door deployments for SIT, SEPT-NS and SEPT-E on Spacecraft B will be in mid
December 4, 2006:
The SECCHI team opened the doors to the SECCHI SCIP-A
instruments and took a few first-light images. Everything went absolutely
smoothly. The three doors opened without incident. The first images look
great even though they were sent down highly compressed to keep the downlink
The EUVI was opened first and an image from each of the four quadrants looked
fine - no major tears or pinholes in the front filters. The sun is close to
being in the center of the CCD, and the resolution is beautiful.
Then we opened COR2 and took an image--also beautiful, although there is a
slight offpoint (which we expected). The exposure time is just about where we
expected, about 3-4 seconds. We then took a pB sequence of 3 images with the
result that streamers could be seen all the way to the edge of the field.
Then COR1 was opened and it was also as expected. A pB sequence shows the
inner corona nicely out to about 2.5 R, which is what we expected.
November 29, 2006:
Both the Ahead and Behind spacecraft performance
continue to perform very well with all subsystems nominal. The instruments on
both observatories continue to perform well. The SECCHI instrument team is
planning to open the doors on the STEREO-A coronagraphs next week and is
completing internal tests.
The definitive orbit solutions from FDF indicate that the STEREO A Observatory
will achieve its required drift rate without further maneuvers. The STEREO B
Observatory will require a 0.2m/s maneuver currently scheduled approximately
December 8th. Both spacecraft will swingby the moon on December 15th, with a
second lunar swingby for STEREO B on January 21st.
The guide telescope has been enabled on both spacecraft. G&C is assessing the
performance of the attitude control algorithms and will upload new parameters
November 22, 2006:
The SWAVES team is now producing daily summary plots through their website at
Follow the links to "data" and then "data plots".
Both the Ahead and Behind spacecraft performance continue to perform very well.
So far, all the planned maneuvers have been completed successfully. The
Mission Operations team is studying the current orbit of the Ahead spacecraft
to see if any more orbital maneuvers are necessary. At least one more delta-V
maneuver is planned for the Behind observatory.
The instruments on both observatories continue to perform well. They were
powered down prior to the P2 maneuvers and then powered back on successfully.
The SEP Central, HET, LET, SIT, SEPT-E, SEPT-NS detectors on IMPACT have been
successfully been powered on and checked out on both observatories. The
Caltech team was able to correlate the first 100 minutes of data from the
STEREO LET instrument on IMPACT with ACE data and the spectra were found to be
A spacecraft roll to calibrate the IMPACT Magnetometer was performed on each
observatory. Initial results show that the test was highly successful.
PLASTIC continues to ramp up their high voltage levels on their MCPs. At the
current HV levels they are starting to see counts from penetrating particles or
photons on their position detectors. The SSDs are also seeing penetrating
particles and photons.
The SECCHI team has completed their decontamination heating of the CCDs on the
COR1 and COR2 telescopes and are preparing to do the same with the EUVI and HI
November 14, 2006:
All the spacecraft subsystems are performing very
well. The Guide Telescope was enabled on the A spacecraft Sunday and
acquired the sun. The GT on the B spacecraft was enabled Monday. In both cases
the GT data looks good and the spacecraft algorithms are correctly using the
data. The spacecraft pointing improved markedly with the GT enabled. There
are more planned tests of the GT and spacecraft control algorithms in December
and more tweaking of the control algorithms.
A complete functional test of the both SECCHI suites was completed at the end
of last week and both suites are working well.
The SEP instruments on the B spacecraft were turned on for the first time
this afternoon. Initial indications are very good.
November 6, 2006:
Both spacecraft went through a 25 minute eclipse as
they went through perigee this morning. The spacecraft behaved nominally
throughout eclipse and are now on their way out to moon radius. The Ahead
spacecraft was intentionally sent to Earth Acquisition mode in order to test
the EA system. The operation of the spacecraft was completely nominal in EA
and recovery from EA to Standby was nominal. The instruments on the A
spacecraft were turned off as part of the EA test. The instruments were turned
back on and are continuing with commissioning activities.
The PLASTIC SSD high voltage has been turned on both spacecraft. The MCP high
voltages have been turn on at low voltage on both spacecraft. The MCP voltages
will be ramped up to operational voltages over the next month.
November 3, 2006 UPDATE:
This is STEREO's second week in Earth
orbit(s). It is still in it's first of four phasing orbits--prior to the first
lunar swingby. So far the planned commissioning activities have occurred
without any serious anomalies. The major deployments of solar
arrays, spacecraft separation, and high gain antennas occurred almost
immediately after launch. Since then, the SWAVES antennas on each observatory
have been deployed -- and SWAVES started producing significant science data.
This week, the significant commission events were the execution of the apogee
propulsive maneuvers on both spacecraft that raised their perigees to altitudes
that are comfortably above the atmosphere. These 'burns' were accurate to
within 0.5% -- that is considered very good considering that the observatories
have not yet been fully characterized. The other significant event was the
deployment of the four meter rigid IMPACT boom on each observatory. The MOPS
and Engineering teams performed other important activities: 1) the High Gain
Antennae were successfully exercised over their full range of motion on both
spacecraft. 2) The software team completed its assessment of observed SEU bit
flips on the C&DH and G&C computers and uplinked a patch (after a change
control board review) to correct an issue in the memory scrub software.
Currently, both observatories are operating nominally. All subsystems and
instruments on both observatories have a GREEN health status. Some IMPACT
detectors are currently saturated, possibly due to the proximity to Earth.
This effect is still being investigated. MAG is seeing higher than expected
offsets, which is correctable in software. SWAVES-Behind observes two
interference signals (100 kHz and 16 kHz) associated with the boom deployment.
With the booms deployed the spacecraft pointing has become very stable with the
pointing much less than 7 arc-seconds. We have ended our 24/7 coverage from
DSN and have gone to our nominal 3 hour tracks per day per spacecraft.
November 3, 2006:
Engineering burns were performed on the C thruster set
of both spacecraft. Both burns were completely nominal so all the thrusters
have been checked out and are working. All the spacecraft subsystems are
November 1, 2006:
Previous item should have reported that PLASTIC was
also partially powered up successfully on both observatories.
The A1 maneuver was successfully completed on both spacecraft.
The two IMPACT booms have been deployed.
The High Gain Antennae were exercised through their full ranges of motion.
October 30, 2006:
Spacecraft subsystems are performing normally. The
SECCHI instrument suites were turned on on both observatories and all telescope
subsystems passed their functional tests. The SWAVES instruments were turned
on, and both sets of antennae were successfully deployed. Parts of the IMPACT
instruments have been powered on.
October 25, 2006:
The twin STEREO observatories were launched at 8:52 p.m. EDT.