SPACE TELESCOPE SCIENCE INSTITUTE Operated for NASA by AURA COS TAGFLASH System Requirements Review CALCOS Requirements Philip E Hodge 14 December 2005

COS TAGFLASH SRR Phil Hodge December 14, 2005CALCOS Requirements Space Telescope Science Institute 2 of 6 Keywords  Requirement 15. CALCOS shall be informed of – TIMETAG mode type (flash or not) – Planned number of flashes – Planned start time of each flash – Planned duration of each flash  Requirement 16. CALCOS shall determine and report the – Actual start time of each flash – Actual duration of each flash – Actual time of median photon event for each flash

COS TAGFLASH SRR Phil Hodge December 14, 2005CALCOS Requirements Space Telescope Science Institute 3 of 6 Update Keywords   Read nominal times and durations of flashes from input header   Use count rate in wavecal region to determine actual start time, end time, and median time of each flash – – A separate program currently exists that will find the start time and end time of each flash   Update keywords in header of _corrtag table with actual values   Use median time as time of flash

COS TAGFLASH SRR Phil Hodge December 14, 2005CALCOS Requirements Space Telescope Science Institute 4 of 6 Determine the Drift  Requirement 13. CALCOS shall incorporate an OSM drift- compensation algorithm that utilizes TAGFLASH lamp flash information to correct science data for OSM drift in each TAGFLASH exposure  Locate the lamp spectrum in the cross-dispersion direction  Extract a 1-D spectrum for each flash  Cross correlate 1-D spectra with template to find offsets of flashes in dispersion direction  Compute coefficients for linear interpolation of drift as a function of time

COS TAGFLASH SRR Phil Hodge December 14, 2005CALCOS Requirements Space Telescope Science Institute 5 of 6 Apply Corrections  Requirement 14. CALCOS shall include the derived OSM-drift corrections in the output _corrtag list and subsequently output extracted spectrum reduced data files  For TAGFLASH exposures: – Compute corrected pixel coordinates, save in new columns in _corrtag table; values in other columns not affected – _flt image created from wavecal-corrected pixel coordinates; image would otherwise be smeared  For conventional wavecals: – _flt image created from uncorrected pixel coordinates – Correction is applied to science data by adjusting the wavelength array for the extracted spectrum

COS TAGFLASH SRR Phil Hodge December 14, 2005CALCOS Requirements Space Telescope Science Institute 6 of 6 Save Flash Spectra  Requirement 17. CALCOS shall extract the individual flash spectra and output them as separate data products  1-D flash spectra are extracted directly from events table, in contrast to science spectra, which are extracted from _flt image  Spectra are written to _lampflash table, one row per flash, using a format similar to _x1d table – Count rate array extracted from uncorrected pixel coordinates – Wavelength array includes drift correction