eSASS derives its heritage mainly from the ROSAT and XMM-Newton data analysis packages. This is also the case for its name:
Drawing from the above acronyms eSASS might thus stand for:
In another line of reasoning, we started out to refer to the eROSITA data analysis software as eROSITA-SASS (with SASS referring to the ROSAT term), which eventually was shortened to eSASS. This also nicely fits with eRASS, another eROSITA acronym, which stands for eROSITA All-Sky Survey, referring back to the RASS (ROSAT All-Sky Survey). It is important to note that while ROSAT provided two different software packages for the pipeline (SASS) and interactive (EXSAS) data analysis, both functions are combined in one package in eSASS. The "Standard" for the first "S" in SASS is not appropriate for eSASS and it was replaced with "Science". As the "e" in this case refer to eROSITA, it's probably best to think of eSASS as standing for:
Go to this page for for details.
You will be able to run eSASS tasks at the command prompt after you executed one of the following setup scripts:
$ source /<my eSASS path>/eSASS4EDR/bin/esass-init.sh
or
$ source /<my eSASS path>/eSASS4EDR/bin/esass-init.csh
eSASS make use of the HEASARC CALDB framework to manage the eROSITA calibration files. This is handled automatically by the eSASS setup script.
"**STOP** Error initializing PIL"
when I run eSASS task X? This is a relatively frequent error message which occurs in the following situations:
plist
for a list of all task parameters. "**ERROR2** YY //YY"
when I run eSASS task X? This error is harmless and it has no impact on the task processing.
evtool
so big? Most of the image's size is comprised of the other extensions in the image file (approximately 63 different tables). Please have a look at the evtool
task documentation to disable such behaviour.
Please refer to this page for further information.
Please refer to this page for further information.
eROSITA generates a CCD frame about every 50 ms. The chopper parameter can be used to specify that only the n-th frame will be read out, stored and sent back to Earth. For example, in order to reduce the telemetry due to bright sources, one can use chopper values > 1. The chopper value can be commanded individually for each of the seven eROSITA cameras. If a chopper value equal to n (>1) is commanded for a camera, then the effective exposure time of that camera of the observation will be reduced by a factor n.
Some of the eROSITA Calibration and Performance Verification (Cal-PV) observations were performed with chopper values different from 1. These observations include Vela SNR, Puppis A, LMC N132D, and a few more. The validation report that comes with each Cal-PV observation specifies if the observation you are interested in was performed with a chopper value different from 1.
An important thing to consider is that the eSASS software version that was used to produce these event lists and that is released in this site, does not account properly for chopper values > 1. The software performs 'double accounting', i.e. for chopper=n, it not only divides the dead time fraction (DEADC) by n, but also cuts away good time intervals (GTI) at the same cadence. Therefore the exposure produced is 1/n the value it should have.
For example, for chopper=2, DEADC will be 0.5, and the GTI fraction will also be 0.5. Therefore the exposure will be 0.25, i.e 0.5x0.5, where it should be 0.5. Therefore, it needs to be multiplied by 2 to bring it to the correct value.