Data description

This chapter provides the detailed description of the CGBM data stored in the CGBM data archive.

The CGBM data archive comprises Scientific data and Auxiliary data.

Scientific data

There are two general types of scientific data: Monitor data and Trigger data.

Monitor data

Monitor data consist of Time History (TH) data and Pulse Height (PH) data.

Time History (TH) data

See also

The TH FITS file

Each CGBM gamma-ray detector collects TH data data with a 1/8(=0.125) sec time resolution in two overlapping energy ranges which correspond to two different gains: high gain (HG) and low gain (LG). Each range has 4 channels.

The nominal TH energy ranges of the three CGBM gamma-ray detectors are (approximate):

Detector Gain Energy range (keV)
HXM1, HXM2 HG 4 ─ 100
LG 60 ─ 3000
SGM HG 40 ─ 1000
LG 550 ─ 28000

The nominal TH channel boundaries of the three CGBM gamma-ray detectors are (approximate):

Detector Gain Channel boundaries (keV)
Ch0 Ch1 Ch2 Ch3
HXM1, HXM2 HG 4 ─ 10 10 ─ 25 25 ─ 50 50 ─ 100
LG 60 ─ 100 100 ─ 170 170 ─ 300 300 ─ 3000
SGM HG 40 ─ 100 100 ─ 230 230 ─ 450 450 ─ 1000
LG 55 ─ 830 830 ─ 1500 1500 ─ 2600 2600 ─ 28000

Note

  1. Since the last channel of the HG range and the first channel of the LG range are partially overlapped, the counts accumulated in these channels are not independent.
  2. EBOUNDS extensions of The TH FITS file contain the same energy boundaries for the entire mission lifetime, i.e. they are not corrected for the gain drift.
  3. TH data are recorded even when HV is off, in which case 0 values are put in the record. There are Good Time Intervals (GTI) fits files which specify the time intervals when HV was above 90% of its nominal value. The TH data near the times where HV was turned on/off are affected by lower HV (HV is increased/decreased gradually near these times).
  4. There might be gaps in TH data.

Warning

  • The EXPOSURE column of the TH data is not corrected for the deadtime. In a future release, we will provide the deadtime corrected exposure time in the EXPOSURE column.
  • The TH data (monitor data) have a known issue regarding a jitter in timing. TIME column of the data could introduce the systematic jitter of several tens of milliseconds (i.e. the difference between the times of successive bins can differ from the nominal 0.125 s by several tens of milliseconds). Although we understand the cause of this timing issue and the way to correct this, the correction has not been applied to the current version. Please be cautious that the TIME column of the data could introduce the systematic jitter of several tens of milliseconds.
  • See all important Caveats for the current release.

Pulse Height (PH) data

See also

The PH FITS file

Each CGBM gamma-ray detector collects PH data with a 4 sec time resolution in two overlapping energy ranges which correspond to two different gains: high gain (HG) and low gain (LG). The HG range has 102 channels and the LG range has 410 channels. The LG range includes the entire HG range, but provides coarser energy binning.

The nominal PH energy ranges of the three CGBM gamma-ray detectors are:

Detector Gain Energy range (keV)
HXM1, HXM2 HG 0.0 ─ 98.304
LG 0.0 ─ 3072.0
SGM HG 0.0 ─ 942.080
LG 0.0 ─ 28672.0

The nominal PH channel boundaries of the three CGBM gamma-ray detectors can be found in the corresponding ascii files:

Note

  1. Since the LG range includes the entire HG range, the counts accumulated in the overlapped channels are not independent, they correspond to the same events but digitized differently.
  2. PH data are recorded even when HV is off, in which case 0 values are put in the record. There are Good Time Intervals (GTI) fits files which specify the time intervals when HV was above 90% of its nominal value. The PH data near the times where HV was turned on/off are affected by lower HV (HV is increased/decreased gradually near these times).
  3. There might be gaps in PH data.

Trigger data

Note

The trigger data are not available in the current release of the archive.

TBD

Auxiliary data

The detailed description of the auxiliary data will be provided later.

The following table briefly summarizes each file type:

Type Name Description
att, iat cgbm_YYYYMMDD.att, cgbm_YYYYMMDD.iat contains the attitude information
hk cgbm_YYYYMMDD.hk contains the housekeeping data related to CGBM detectors
orb cgbm_YYYYMMDD.orb contains the orbit information
tim cgbm_YYYYMMDD.tim contains the time correction data
gti cgbm_YYYYMMDD_[det].gti contains good time intervals for each detector