The total background due to all non-source contributions is 0.28 ct/s above 0.5 keV and 0.19 ct/s above 1 keV. Background is not measured simultaneously, and must be estimated from data accumulated over source-free exposures.
A time-dependent build-up of ice (water) on the detector surface occurred because of cryopumping of ambient outgassing material onto the 100 K detector. It was periodically defrosted by heating to 220 K at the beginning of a series of three days of observations. Each defrost reduced the total amount of ice that returned, such that after 9 months the ice covering was almost gone. The ice covering is parameterized by an ice parameter that varies from a low value of 0.05 to a high early on of 4.58. A model has been developed that predicts the ice parameter as a function of time, and is used to obtain the correct response matrix for any given observation. The uncertainty in this ice parameter varies throughout the operational lifetime, and is greatest at the beginning. More information on the ice modeling procedure can be obtained in Arnaud, Szymkowiak, and White (1989, HEAO Newsletter, Vol. 1, No. 2) and Christian, Swank, and White (1992, Legacy: the HEASARC Newsletter, Vol. 1, No. 1).
Further information about the SSS calibration and the associated uncertainties can be obtained from VIMAT, by typing `vimat help`.
The cryogen keeping the SSS at its operating temperature of 100 K ran out, as expected, in October 1979, and no more observations were possible.
There is at least one spectrum per SSS observation of each target. If the observations covered an interval that extends over more than one (UT) day, then there is a spectrum accumulated for each day. The spectra are not background-subtracted. Detector response matrices and background spectra are made using the VIMAT program, or from within BROWSE using the XSPEC command.
Lightcurves: There is a background-subtracted 81.92 s time resolution light curve in the 1.0-4.0 keV band covering the time interval of each spectrum.
Associated Products: The Einstein monitor proportional counter, MPC, operated in the 1-15 keV band, with eight pulse height channels. It was a mechanically collimated detector with a full width half maximum field of view of 45 arc minutes.
There is one MPC spectrum accumulated to match each SSS spectrum (with the small number of exceptions noted above where there are no matching MPC observations). The spectra are not background-subtracted. Background spectra and the detector response matrix (the latter is considered to be valid for the entire mission) can be extracted using the VIMAT program.
There are also background-subtracted 40.96 s time resolution light curves in the 1.0-15.0 keV band covering the time interval of each spectrum.
Notice that, due to the differing instrumental observing constraints and particle background thresholds, the SSS and MPC data products are only quasi-simultaneous. The start and stop times referred to in the parameters description refer specifically to the SSS observations.
* `min count rate` - minimum count rate during the observation * `Max count rate` - maximum count rate during the observation.
'bes' for X-ray binary with Be star primary: e.g., Gam Cas. 'blk' for X-ray binary with black hole primary: e.g., Cyg X-1. 'cluster' for cluster of galaxies: e.g., A 2029. 'cvs' for cataclysmic variable: e.g., AM Her. 'gal' for galaxy or quasar: e.g., 3C273. 'lmxb' for low-mass X-ray binary: e.g., Cyg X-2. 'pulsar' for pulsar: e.g., Cen X-3. 'rscvn' for RS CVn active binary system: e.g., AR Lac. 'snr' for supernova remnant: e.g., sn 1006. 'star' for miscellaneous varieties of galactic stars not belonging to the other stellar categories: e.g., tau Sco. 'mispt' for observations made at incorrect co-ordinates (i.e., mispoints).
HEASARC User Hotline.