Important notice about STEREO Behind
Important Notice About Reduced STEREO Science Operations
Update: Communications with the STEREO Behind spacecraft were
interrupted on October 1, 2014 immediately after a planned reset of the
spacecraft performed as part of a test of the solar conjunction operations
described below. The spacecraft telemetry indicated an anomaly in the guidance
and control system, but this is still being evaluated. No further
communications have been successful since Oct. 1st. Follow
this link for more information.
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. Only
limited instrument operations
can be supported while the antennas are off-pointed. No recorder playback will
be possible during this time. Only real-time data will be available during the
70 meter Deep Space Network contacts, on the order of a few hours per day. A
very low rate telemetry stream from the in situ and radio instruments
will be recorded for eventual playback.
Side lobe operations have started on the STEREO Ahead spacecraft, and will
start on the Behind spacecraft on December 1, 2014. The two
spacecraft will remain in this state for just over a year, with normal
operations resuming in January 2016. As has been known since before launch,
there will also be a several month period during this time when no
communications will be possible with either STEREO spacecraft as they pass
behind the Sun, simply due to too much interference from the Sun itself.
More information about the schedule of operations can be found on the STEREO
observations calendar page.
There's also a
NASA article describing the situation with the STEREO
spacecraft during this period, with a
question and answer section.
Last Revised: Friday, 07-Nov-2014 22:21:23 GMT
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