SECCHI Data User Guide

$Revision: 1.30 $, $Date: 2014/10/17 19:47:42 $

Contact mvi at nrl.navy.mil

1. Web query is available at http://secchi.nrl.navy.mil. This method offers the most options for building a search query.
2. Using Solarsoft/IDL you may use xsecchi_vso_ingest.pro to retrieve data from the STEREO Science Center over a socket. Note that this tends to be a slow process (about 4.7MB, or 1 file, per minute).

After you have downloaded files, it is recommended to organize them in a way which replicates the original archive. The routine SCCINGEST will help you do this. The basic steps are as follows:

1. Download the data into a temporary directory (which may contain subdirectories).
2. Define the environment variable $SECCHI_LZ to point to the top of the directory tree that will contain the data.
3. Run IDL> sccingest, DIRECTORY where DIRECTORY is the name of the temporary directory.

For example, suppose that you had copied a bunch of SECCHI files to the temporary tree "c:\mytemp", and wanted to store them within your local archive "c:\secchidata". You would enter the following commands:

IDL> setenv,'SECCHI_LZ=c:\secchidata'	;If not already done
IDL> sccingest, 'c:\mytemp'

Once you have the SECCHI FITS archive available to you locally in $secchi or $SECCHI_LZ, there are two ways to retrieve lists of FITS files:

1. The fastest way to query for large intervals of SECCHI data is using the summary files and scc_read_summary.pro which returns an array of structures with the summary file information. After retrieving this information, you may use sccfindfits.pro to retrieve path information for each file.
2. If you are doing a more targeted search and/or want to refine your search using more parameters, there is scclister.pro. This returns a structure of filenames (including path) for Ahead and/or Behind. (Note: For date ranges more than a few days, as implemented, this takes a long time.)
3. Finally, it is possible to do an image database query from IDL using sqdb.pro. (Note: This method only works at NRL.)

Types of SECCHI Images

For any of these queries, the user should be aware of the various types of images which may be returned:

• Spacecraft: Ahead or Behind
• Telescope/Instrument: EUVI, COR1, COR2, HI1, HI2
• Destination: SSR1 (synoptic program), SSR2 (event partition), Spaceweather/Beacon (low resolution), Realtime Downlink (early ops only). NOTE: During Sidelobe operations, all images come down the Beacon channel.
• Data Source: Usually LZ
• Data Type:
  1. Intensity (img): EUVI, HI, and COR2 DOUBLE (two polarizer positions)
  2. Polarized (seq): COR1 and COR2 single polarizer position images
  3. Calibration (cal): LED, DARK, etc.
  4. Intensity+Polarized: both img and seq (COR2 only)
  5. TBPP: Total Brightness and Percent Polarized images in $SECCHI_P0 at NRL
  6. EUVI Quadrant: 171A, 195A, 284A, 304A
  7. COR Polar: Usually 0, 120, or 240

You can tell what kind of image you have by looking at the last 5 characters of the filename root:

YYYYMMDD_HHMMSS_ABCDE.fts

A=Type, B=Destination, CD=Telescope, E=Spacecraft.

Go to http://secchi.nrl.navy.mil/images and browse the categories that appear in the left-hand sidebar.

SCC_MK_IMAGE.PRO will turn (almost) any SECCHI FITS file into a pretty picture using default settings. To use this routine, you just supply it with a SECCHI FITS file name, and it will return to you a beautiful, byte-scaled, "pretty" data array. Example (incl. comet!):

IDL> purdy_image=scc_mk_image('$secchi/lz/L0/a/img/cor2/20070608/20070608_013730_d4c2A.fts')
IDL> tv,purdy_image

You can choose the output size (default is 1024), turn logo/date-time stamp off, or control size of stamp. See the pro header for other options.

Using SECCHI_PREP for pretty pictures

To return 512x512 images corrected only for exposure duration and Binning, and data values in header not updated (quicker):

IDL> SECCHI_PREP, filenames, headers, images, OUTSIZE=512, /NOCALFAC, /CALIMG_OFF, /UPDATE_HDR_OFF, /EXPTIME_OFF 

IDL> bkg = scc_getbkgimg(secchi_hdr)

; Options   : /SILENT = Don't print out informational messages
;             /TOTALB = Look for the total brightness background
;             /INTERPOLATE = Interpolate between background images.
;             /DAILY  = Use daily median background image instead of monthly minimum
;             /CALROLL= Use combination of monthly minimum and calibration roll
;                       backgrounds.  These backgrounds may show some problems
;                       during the long gap between calibration rolls in mid to
;                       late 2007
;             /RAW_CALROLL = Use raw calibration roll backgrounds.  This option
;                       is not recommended, and is included mainly to support
;                       generating the combined monthly/calroll backgrounds.
;             OUTHDR  = returns the header of the background image
;   	      /MATCH  = Match state of bias, exptime, summing, size of output to input hdr
;   	      /ROLL = if difference in CROTA is GT 1 deg, rotate bkg to match input
;   	      /NONLINEARITYCORRECTION = apply COR2 double exposure non-lineariy correction (experimental)

IDL> annotate_image,filename

Input can be filename of an image or MVI file, or window index. Further details here

SPICE is a suite of software and data products which describe solar system geometry in relationship with NASA spacecraft. The STEREO SPICE Toolbox is part of the stereo/gen/idl/spice sub- directory of the SolarSoft distribution. It is described in Reading STEREO Ephemerides as SPICE Kernels (pdf). The necessary SPICE DLM files are set automatically when you have one of the STEREO instruments or SSC in your $SSW_INSTR.

It should no longer be necessary to use the IDL -32 option with 64-bit linux or Solaris computers; however, it is still necessary with MacOS as of 7/20/09.

You may use the SSW IDL procedure getsccinfo.pro to obtain statistics about the SECCHI archive, either Level 0.5 FITS files or raw (unprocessed) image telemetry files. You may specify one or more telescopes, volume, number of files, SSR partition, start date, and number of days. See the procedure for details. The procedure reads in data files from $SCC_DATA, which are updated daily. It returns a vector of cumulative totals day by day.

It is helpful to think about HI pipeline in terms of the files which come down from the spacecraft. HI images are sums of many separate readouts (images). For each readout, a separate "image" file is sent down. These are just like regular images except without the image--just the header. For the actual image data after all the readouts have been summed, two files are sent down. One has the high-word data, the other the low-word data. They both have the header for the last readout in the series. All of these files are processed serially on the ground, the image data being processed last. As the headers are ingested, information for the extended header is retrieved and saved until the file is written. In the final FITS file, the image data is the combined high and low-word images, and the main FITS header includes information about all of the previously-processed headers for this image. More detail about the individual exposures is in an extended header. [IDL> exthdr=mrdfits(filename,1)]

Each individual header which comes down is treated in the pipeline just like a regular image, except there is no file written. The pipeline creates a FITS header, and the information is put into the database, just like every other image. Since these files have no image, NAXIS=NAXIS1=NAXIS2=0.

There are two ways to access HK telemetry from SECCHI.

• Web query via http://stereo.nrl.navy.mil/secchi_database.html.
• Using IDL at NRL. The function get_scc_hk.pro allows the user to query for any telemetry point that is in our database at a specified time resolution and optionally write the result to a csv file:

  IDL> s=get_scc_hk('b','temp','HBHI1CCDT,HBHI2CCDT','20081001','20081031',write='.')
  

  For Software Event messages, there is another function idl/database/gethkevents.pro which returns a structure matching the field names in the HK Events Table Definition. Keywords allow to query specific Event Codes (see HKEVENTCODE mnemonic definition), Software Subsystem, first data code, string in event message, or uploaded filename:

  
  IDL> ev=gethkevents('a','2006-11-01 12:34:12','2006-11-05 23:12:09',code=23)