Page 1 17-Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover HESSI LEVEL 0 DATA J MCTIERNAN

Page 2 17-Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover LINKS: This document: HESSI Level 0 Data Handling: HESSI Quicklook Data Products: HESSI Flare List: HESSI File database:

Page 3 17-Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover

Page 4 17-Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover HSI_CONTACT2FITS IDL routine, runs automatically in SOC (Science Ops Center) INPUT: Telemetry files (packets from spacecraft: Vc1 is stored state of health, Vc3 is stored science data) Orbit Data: Eclipse and SAA info, and state vectors Calibration Files in $SSW/hessi/dbase

Page 5 17-Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover HESSI Data Products LEVEL 0 DATA FILES: usually 1 per orbit, telemetry packets with appended catalog; FITS binary extensions. “hsi_yyyymmdd_hhmmss_nnn.fits “ Plot files (PNG format), images, spectra, and count rate plots. Daily Catalog files, online: “hessi_catalog_yyyymmdd.fits”, available with SSW. HESSI Flare List,: “hessi_flare_list.fits”, also an ascii file: “hessi_flare_list.ascii” Database file, contains file names, time ranges: “hsi_filedb.fits” CD list file, lists files on each CD. Clock Sync file, syncs spacecraft time to UT.

Page 6 17-Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover PROCESSING PACKETS: All Vc1 and Vc3 packets are read into an array Check for bad packets, check for Reed-Solomon ‘uncorrected bit error’, check for bad app_id, bad collection time (I.e. packets with times far out of range, or packets with times out of sequence in comparison with valid sequence counts). Bad packets are flagged, but retained. Given packet time range, the appropriate orbit data is input, level 0 file start and end times for each orbit are determined: files start and end in eclipse periods. Then for each orbit:

Page 7 17-Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover FOR EACH ORBIT: The file database is checked to see if there is data for this file time range from previous contacts. If there is previous data, those packets are input and included. Check for duplicate packets by comparing packet headers. Duplicates are deleted, with packets flagged as bad deleted preferentially. Now we have all of the packets for a given orbit. If there are more than packets, then the packets are split into multiple files. (To keep the maximum file size below 50 Mb) Write files: hsi_yyyymmdd_hhmmss_nnn.fits. The minimum file time range is 20 seconds (or 5 roll periods, the time interval of saved ephemeris data). If Previous files were found for the same time interval the version number ‘nnn’ is incremented, to avoid overwriting.

Page 8 17-Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover Update HSI_FILEDB Each file is recorded as an entry in the filedb structure. This is written into a FITS file, which is opened and read and rewritten for every ground station contact. The database file for all level 0 data will be distributed as part of the software. Contents: version = A version number file_id = file name orbit_start, orbit_end = Orbit number (GDS) at start and end of the file start_time, end_time = data start and end times status_flag = set to -1 if the file has been discarded, and the packets are contained in another file, set to 0 if the file exists npackets = Number of packets clock_drift_start, clock_drift_end = the value of the clock drift at file start and end

Page 9 17-Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover For Each Level 0 File: Observing Summary Spin-averaged count rates in 9 energy bands, summed over detectors, 4 second (one spin period) time resolution. Particle detector rates, 4 sec. Modulation variance, 2 Coarsest collimators. S/C position and velocity, 20 sec (5 spin periods) resolution. 10 arcsec resolution S/C pointing estimate and Roll period estimate, 1 sec (1/4 spin period) time resolution. Flags for: ['SAA_FLAG', 'ECLIPSE_FLAG', 'FLARE ‘, ’NON_SOLAR_EVENT', 'FRONT_RATIO', 'DECIMATION', 'IDPU_CONTROL_VERSION_NUMBER’, 'CRYOCOOLER_POWER', 'COLD_PLATE_TEMP', 'IDPU_TEMP', 'COLD_PLATE_SUPPLY', 'HV28_SUPPLY', 'ACTUATOR_SUPPLY', 'FAST_HOUSEKEEPING', 'SC_TRANSMITTER', 'SC_IN_SUNLIGHT', 'SSR_STATE', 'ATTENUATOR_STATE’, ‘LIVE_TIME’]

Page Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover Finding Flares: Use 1 min running average in 12 to 25 keV range to determine threshold count rate. Intervals with count rates from 12 to 25 keV greater than the threshold are flagged. Threshold is 5 sigma. (All thresholds are expected to be changed after we see real data). Verify Solar events by checking: 1) count rates in each detector must be 5 sigma above background. 2) Modulation variance must be greater than ) Front-Rear count ratio must be greater than background level For events determined to be solar, the above criteria can are used to adjust the flare end time.

Page Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover Flares in multiple files: For each event, the background count spectrum is saved. At the start of the flare-finding process, information from the previous file is included: The last 1 minute of count rates, is appended to the start of the data array used for threshold finding. If the flare_at_EOF flag is set for the previous file, then the background spectrum for that flare is used for flare interval determination.

Page Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover Flare Position: Flare position is found using a back-projection image for the peak 4 second interval of the flare. 64 X 64 pixels - 35 arcsec resolution.

Page Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover HESSI Flare Position Image

Page Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover HESSI Catalog: Flare List Id number. Start, peak and end times, in energy range [12.0, 25.0] keV (note peak time is start time of peak 4 sec interval) Peak count rate, counts/sec/segment and total counts. Background Count rate and Time Range. Highest energy of observed photons. Flare position, arcsec from Sun center. Flags for flares that start/end in Eclipse or SAA, flares at file SOF, EOF. Solar-Non-solar event flag. Detector Id's (Fronts only are used for flares, both can be used for others). File(s) which have the data.

Page Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover Quicklook Spectra and Images “Semi-Calibrated” (I.e., diagonal response matrix) photon spectrum at flare peak, 392 energy channels, dE = 1 to 100 keV, larger at higher energies, with 1 keV channels near 511 and 2200 keV. Images at flare peak, 5 arcsecond spatial resolution, CLEAN algorithm, in the energy bands given by the Observing Summary, [3, 6, 12, 25, 50,100,300,1000,10000, 20000] keV

Page Dec-2001 HESSI High Energy Solar Spectroscopic Imager Use or disclosure of data contained on this page is subject to the restrictions on the volume cover Other Data Products: Daily Catalogs are created or appended if level 0 files from that day are processed. File database file, hsi_filedb.fits is updated Whole Mission flare list file hessi_flare_list.fits is updated Clock drift file hse_clk_drift_cat is updated Files with filedb.status = -1 (I.e. files which had data for the same time period but have been replaced by newer versions) are deleted.