The purpose of this page is to describe the different standard extensions of the data and source products as they are produced by the eROSITA Science Analysis Software System (eSASS).
On this page
TIME R*8 The same as FRAMETIME (see below). The accuracy
limitations mentioned under FRAMETIME's column
description also apply to this column. By default,
the TIME values will be non-randomised and not
baricentre-corrected; these corrections will be
applied by interactive tasks on a case by case basis
RA, DEC R*8 J2000, calculated from attitude, RAWX, RAWY, and
SUBX, SUBY. (Datatype was originally designed to
be I*4.)
X, Y R*8 Sky projection coordinates, of pixel size 0.05 arcsec.
Units and origin as defined in WCS keywords.
(Datatype was originally designed to be I*4.)
PI R*4 For each pixel of an event pattern, the PI
column will contain the corrected total energy
in eV (positive for main event, negative for all
other pixels).
EV_WEIGHT R*4 Intended to contain a vignetting correction
factor (and potentially other corrections), but
presently unused.
RAWX, RAWY I*2 Position of the event on the CCD pixel grid.
See Properties of the CCDs relevant for processing,
link points to Early Data Release, since nothing has changed since then
SUBX, SUBY R*8 Reconstructed fractional CCD pixel position of
the event centroid. (Datatype was originally
designed to be I*1.)
See Properties of the CCDs relevant for processing,
link points to Early Data Release, since nothing has changed since then
PHA I*2 Raw event amplitude [adu]
PAT_TYP I*2 Pattern type: number of pixels in the pattern,
positive (1-4) for valid, negative for invalid
patterns, same value for all the pixels in the
pattern, 0 indicates that pixel was ignored
because PHA was too low (for a more detailed description s. here)
PAT_INF I*1 Pattern information (for a more detailed description s. here):
For valid patterns: 3 decimal digits p d q
p: position of the pixel in the pattern (0-2)
d: direction of the pattern (1-4)
q: quality of the pattern (0-9)
For single pixels: tr q
tr: trailing pixel info: precursor distance (<26)
q: quality, with additional information about
diagonal pixel(s)
For invalid patterns:
- if larger than 4 pixels: number of pixels with MIP-like PHAs
- if consisting of 2-4 pixels: PAT_INF = p1 + p2 + p3, with
p1 = 1 if pattern is not recognizable, otherwise p1=0
p2 = 2 if touching an insensitive area with main component, otherwise p2=0
p3 = 4 if likely to consist only of noise events, otherwise p3=0
- if consisting of 1 pixel:
PAT_INF = 2 if single touches insensitive area
PAT_INF = 8 if only present because of diagonal location
PAT_INF = 9 if on pixel set to ‚bad‚ on ground
TM_NR I*1 Telescope module, in the range 1-7.
FLAG I*4 Although this appears as an integer, the
software treats it like a binary flag mask,
with bits described in the following section.
FRAMETIME R*8 Each CCD is read approximately 20 times a
second. Each readout frame can be assigned a
definite time, but for reasons of telemetry
economy this must be reconstructed a posteriori.
This value, expressed in units of seconds since
the reference time given in the MJDREF keyword,
occupies the FRAMETIME column. Note firstly that
this value is only accurate to about 10 ms (the
limitation imposed by the poor precision of the
so-called subseconds counter), and is also
subject to the slow drift (about 14 ms per day,
reset whenever it approaches 1 second in total)
of the spacecraft clock; and secondly that, as
a reconstruction, it is subject to occasional
failure (resulting in NULL values) or error
(which we attempt to catch and correct).
RECORDTIME R*8 This is the spacecraft clock value of the
telemetry frame that contains the event. The
units and offset are the same as FRAMETIME and
TIME. It has lower accuracy (typically 1-3
seconds) than FRAMETIME but, since it is a direct
telemetry value, it is more reliable.
Note that not all the flag bits are presently defined; and not all of the defined ones are in use.
Note that the PHA_QUALITY_? bits are intended for internal communication between tasks within the pipeline. It is not intended that users should filter on these. If you do so, you may get unexpected results.
| ## | HEX | Name | Written by | Remarks |
|---|---|---|---|---|
| Owner flags: | ||||
| 0 | 0x1 | MPE_OWNER | EVATT |
(0 means MPE has rights, 1 not) |
| 1 | 0x2 | IKI_OWNER | EVATT |
(0 means IKI has rights, 1 not) |
| Information flags: | ||||
| 4 | 0x10 | TRAILING_EVENT | ? |
Event has a precursor in the same CCD frame along readout direction. (Not currently set by any task.) |
| 5 | 0x20 | NEXT_TO_BORDER | EVPREP |
Event lies on a CCD pixel at the CCD edge. |
| 8 | 0x100 | NEXT_TO_ONBOARD_BADPIX | FTFINDHOTPIX |
|
| 9 | 0x200 | NEXT_TO_BRIGHT_PIX | FTFINDHOTPIX |
|
| 10 | 0x400 | NEXT_TO_DEAD_PIX | FTFINDHOTPIX |
|
| 11 | 0x800 | NEXT_TO_FLICKERING | FTIFNDHOTPIX |
|
| Rejection flags: | ||||
| 12 | 0x1000 | ON_FLICKERING | FTFINDHOTPIX |
|
| 13 | 0x2000 | ON_BADPIX | FTFINDHTOPIX |
|
| 14 | 0x4000 | ON_DEADPIX | FTFINDHOTPIX |
|
| 15 | 0x8000 | OUT_OF_FOV | EVPREP |
|
| 16 | 0x10000 | OUTSIDE_QUALGTI | QUALGTI |
This bit is not currently set in the pipeline. |
| 17 | 0x20000 | OUTSIDE_GTI | EVPREP |
|
| 18 | 0x40000 | PRECEDING_MIP | EVPREP |
Event has a MIP precursor in the same CCD frame along readout direction. |
| 19 | 0x80000 | MIP_ASSOCIATED | None |
|
| Quality flags: | ||||
| 24 | 0x1000000 | PHA_QUALITY_1 | EVPREP |
For internal pipeline use. |
| 25 | 0x2000000 | PHA_QUALITY_2 | EVPREP |
For internal pipeline use. |
| 26 | 0x4000000 | PHA_QUALITY_3 | EVPREP |
For internal pipeline use. |
| Corrupted data: | ||||
| 29 | 0x20000000 | ARTEFACT | EVPREP |
Events in the frame are mostly ‘barcode’ or ‘space-invader’ camera artefacts. |
| 30 | 0x40000000 | CORRUPT_EVENT | EVPREP |
Assigned if various values in the telemetry are out of possible limits. |
| 31 | 0x80000000 | CORRUPT_FRAME | EVPREP |
Assigned if frame-specific values are out of possible limits. |
While it is possible to select various subsets of events with these flags, not all such selections are supported by the downstream pipeline. If, e.g. the TRAILING_EVENT and/or PRECEDING_MIP flags were selected, then the derived fluxes would not be correct.
There are one or two points about these that should be mentioned. Recall that a CCD frame is read from each of the 7 cameras about 20 times a second. Each frame is associated with a timestamp and will typically be expected to record a handful of cosmic x-ray photons, each of which can generate charge in up to 4 adjacent CCD pixels. Although eROSITA can transmit information about each pixel with charge separately, usually the information is compressed to economise on telemetry. Each such candidate photon is referred to as a ‚raw event‚. Task EVPREP assigns flag bits to any events which are for one reason or another considered suspect.
START R*8 Start and stop times of good time intervals;
STOP R*8 times as defined in TIME column of EVENTS extension.
TIME R*8 Times as defined in TIME column of the EVENTS extension.
RA R*8 RA [deg] of optical axis of telescope n.
DEC R*8 DEC [deg] of optical axis of telescope n.
ROLL R*8 Roll angle (assumed to be the counter-clockwise
angle between the north direction in the J2000 coordinate
system and the X direction of the RAWX/RAWY coordinate system.
Note that the north direction is assumed to be the real north
direction and not the projection of the north vector through
the telescope on the detector.
TIME R*8 Times as defined in TIME column of the EVENTS extension of
telescope n. (TIME refers to middle of validity interval.)
DEADC R*4 0…1 (livetime/ontime); corresponds to the
FRACEXP column of XMM EXPOSURE extensions
or FCT of SASS file LFTIMX.
RAWX I*2 Detector pixel coordinate of telescope n.
RAWY I*2 Detector pixel coordinate of telescope n.
YEXTENT I*2 Extent of bad column in y direction.
TYPE I*2 1=Hot; 2=Flickering; 3=Dead.
BADFLAG I*2 1=uplinked; 2=from CALDB; 3=from file.
TIMEMIN R*8 Start of time window in which pixel is bad.
TIMEMAX R*8 End of time window in which pixel is bad.
PHAMIN I*2 Lower bound of the PHA range over which pixel is bad.
PHAMAX I*2 Upper bound of the PHA range over which pixel is bad.
PHAMED R*4 Median of PHA values (optional).
These contain a selection of the so-called housekeeping (HK) quantities transmitted in the telemetry, plus some quantities derived by the pipeline. For every telescope n the HKs are organised into four extensions designated by numbers m = 1, 2, 3 and 5, according to the pattern of organisation in use by the onboard software.
TIME R*8 Times as defined in TIME column of the EVENTS extension of telescope n.
Recordtime R*8 Same as RECORDTIME in the EVENTS extension.
PxPROCMODE Byte Processing mode; 0: IDLE, 1: work mode, 2: calc offset, 3: calc noise,
4: all singles, … , 9: environment mode 1, 10: environment mode 2.
PxPROCOPTS I*4 Options for program control; 1: always send frame times
PxTMFRAMES R*4 Telemetry frame counter.
PxCCDFRAMES R*4 Number of processed CCD frames.
PxEVTCTR R*4 Event counter.
PxMIPCTR R*4 MIP counter (number of pixels affected by MIP).
PxFWSTEPCT R*4 Step counter (executed).
PxFWSTAT Byte Status of filter wheel.
PxCHOPPER R*4 Specifies what number CCD frame should be processed.
PxSPLT2NOI R*4 Split to noise ratio.
PxEVTQLIMT R*4 Event quota limit.
DxPROCMODE I*2
DxPROCOPTS I*2
DxFWSTAT I*2
RFRAMETIME R*8
QRFRAMETIME I*2
DETSTAT I*2
TIME R*8 Times as defined in TIME column of the EVENTS extension of telescope n.
Recordtime R*8 Same as RECORDTIME in the EVENTS extension.
FWHEEL Byte Position of filter wheel; 0: closed, 1: open, 2: filter, 3: calibration.
CxFWPOS Byte Position of filter wheel; 8: filter, 12: open, 13: calibration, 14: closed, 15: moving.
CxHVFWSW Byte Switches for HV, filter wheel converter and filterwheel position sensors.
CxSTPVOLT R*4 Voltage of stepper motor.
PxMIPDELN R*4 MIP deletion area to the north.
PxMIPDELS R*4 MIP deletion area to the south.
PxMIPDELOW R*4 MIP deletion area to the east and west.
PxMIPIMGMX Byte MIP image (time exposure) maximum.
DxFWPOS I*2
RFRAMETIME R*8
QRFRAMETIME I*2
TIME R*8 Times as defined in TIME column of the EVENTS extension of telescope n.
Recordtime R*8 Same as RECORDTIME in the EVENTS extension.
PxFWDELAY R*4 Overshoot.
PxENVTAB R*4 Table index for selected ENV (dynamic pair).
CxTCCDPT R*4 CCD temperature
DxENVTAB I*2
RFRAMETIME R*8
QRFRAMETIME I*2
TIME R*8 Times as defined in TIME column of the EVENTS extension of telescope n.
Recordtime R*8 Same as RECORDTIME in the EVENTS extension.
PxMIPTHR R*4 Data processing, mip threshold.
PxPRIMTHR R*4 Data processing, prime threshold.
PxFWSTEPS R*4 Number of steps til next stop.
PxSPLTCT R*4 Slit event counter.
PxEVTBMAX R*4 Event-R/P filling level maximum.
PxOUTBFREE R*4 Output R/P: free places.
PxMIPCRTPT R*4
DxMIPTHR I*2
DxPRIMTHR I*2
DxMIPCTRPT I*2
RFRAMETIME R*8
QRFRAMETIME I*2
This records spatial selections by task EVTOOL.
SHAPE A*16 Shape of region: circle, rectangle, ellipse, box.
XC R*8 X coordinate of center in degrees.
YC R*8 Y coordinate of center in degrees.
R R*8 Size of region in degrees.
ROTANG R*8 Rotation angle.
Cumulative sky area vs. limiting flux written by task ERSENSMAP.
LIMFLUX R*4 Flux limit in erg/cm²/s
SKY_AREA R*4 Sky area in square degrees
Count rate and corresponding area within which a source of this count rate can be detected, written by task APETOOL.
LGCR R*4 Logarithm of count rate
AREA R*4 Area in square degrees
All of the extensions in the event list share a common set of keywords (apart from obvious differences such as the EXTNAME keyword). This link provides the information about these header keywords.