Good Time Intervals (GTI)
and the Mission Timeline (MTL)
| Filename | Description | Content | SDP Pipeline |
|---|---|---|---|
| acis_flt1.fits | good time intervals | GTI | ACIS1 |
| hrc_std_flt1.fits | good time intervals | GTI | HRC1 |
| acis_mtl1.fits | mission timeline | MTL | ACIS1 |
| hrc_mtl1.fits | mission timeline | MTL | HRC1 |
| hrc_dtf1.fits | HRC dead time factor | DTFSTATS | HRC1 |
Good Time Intervals
| Filename | Description | Content | SDP Pipeline |
|---|---|---|---|
| acis_flt1.fits | good time intervals | GTI | ACIS1 |
| hrc_std_flt1.fits | good time intervals | GTI | HRC1 |
Description:
The GTI file contains the start and stop times of all accepted time intervals over the observation. This L1 product is used to filter the L1 events at the start of L2 in order to determine the standard set of photons for the observation. It is the photons that pass this time filter that are further processed in L2. When the event file is filtered, the GTI filter is also merged with the time subsection extension of the event list as a dynamic record of the current set of time filters applied to the data.
The "good times" are periods when observing conditions were good; they fall between the TSTART and TSTOP. The two principal causes of a bad observing period are: (1) bad aspect solution, and (2) high background. Users may wish to create a more restrictive set of GTIs if they require a very low background (e.g. for extended source analysis). The tool dmgti can be used for this.
Creator pipeline: acis_L1
dmgti - GTIs are built on a per-chip basis in the pipeline.
GTI-specific columns:
| Column Name | Units | Description |
|---|---|---|
| START | seconds | Good time interval start time |
| STOP | seconds | Good time interval stoptime |
Mission Timeline
| Filename | Description | Content | SDP Pipeline |
|---|---|---|---|
| acis_mtl1.fits | mission timeline | MTL | ACIS1 |
| hrc_mtl1.fits | mission timeline | MTL | HRC1 |
Description:
The mission timeline (MTL) file contains the telescope's housekeeping and configuration information, such as pointing relative to the sun's limb, particle flux, aspection solution status, and grating position. For HRC files, voltage monitors and image diagnostics are also included.
The contents of the MTL are specified by a lookup table which is determined by science input. The MTL also defines good observing times, which is used in creating the GTIs.
Creator pipeline: acis_L1
The MTL tool, mtl_build_table, is not distributed with the CIAO software.
MTL-specific columns:
| Column Name | Units | Description |
|---|---|---|
| time | seconds | - |
| Point_SunLimbAng | degrees | Pointing angle from Solar Limb |
| Point_MoonLimbAng | degrees | Pointing angle from Lunar Limb |
| Point_EarthLimbAng | degrees | Pointing angle from Earth Limb |
| Point_RamVectorAng | degrees | Pointing-Ram angle |
| Dist_SatEarth | meters | Satellite-Earth distance (from Earth center) |
| SCP4 | Hz/cm**2/sr | Sci coincidence counter P4 rate |
| SCP8 | Hz/cm**2/sr | Sci coincidence counter P8 rate |
| SCH4 | Hz/cm**2/sr | Sci coincidence counter H4 rate |
| SCH8 | Hz/cm**2/sr | Sci coincidence counter H8 rate |
| SCE150 | Hz/cm**2/sr | Sci coincidence counter E150 rate |
| SCE300 | Hz/cm**2/sr | Sci coincidence counter E300 rate |
| SCE1300 | Hz/cm**2/sr | Sci coincidence counter E1300 rate |
| SCE3000 | Hz/cm**2/sr | Sci coincidence counter E3000 rate |
| SCINT | Hz/cm**2/sr | Sci coincidence counter INT rate |
| SCP25 | Hz/cm**2/sr | Sci coincidence counter P25 rate |
| SCP41 | Hz/cm**2/sr | Sci coincidence counter P41 rate |
| SCH25 | Hz/cm**2/sr | Sci coincidence counter H25 rate |
| SCH41 | Hz/cm**2/sr | Sci coincidence counter H41 rate |
| IMHVLV | - | (HRC) Imaging Bot MCP HV Monitor |
| IMHBLV | - | (HRC) Imaging Bot & TOP MCP HV Monitor |
| SPHVLV | - | (HRC) Spect Bot MCP HV Monitor |
| SPHBLV | - | (HRC) Spect Bot & Top MCP HV Monitor |
| img_diam_rms | arcsec | Aspect image RMS diameter |
| img_roll_rms | arcsec | Aspect image RMS roll err |
| target_offset | arcsec | Target offset from nominal |
| rw_speed_bad | - | Reaction wheel speed bad |
| asp_sol_status | - | Aspect solution quality |
| HRMA_CAPGRAD0 | K | - |
| HRMA_CAPGRAD1 | K | - |
| HRMA_CAPTEMP | K | - |
| HRMA_FRWDTEMP | K | - |
| HRMA_AFTTEMP | K | - |
| HRMA_TEMP | K | - |
| OBA_PERIGRAD0 | K | - |
| OBA_PERIGRAD1 | K | - |
| THR_PIX | - | (ACIS) |
| EVTSENT | - | (ACIS) |
| EXPNO | - | (ACIS) |
| DETNAM | - | - |
| DATAMODE | - | - |
| READMODE | - | (ACIS) |
| FP_TEMP | - | - |
| GRATING | - | - |
| DET_HV | - | (HRC) High Voltage ON or OFF |
| MOVING | - | Is SIM moving? |
| DTF | - | (HRC) |
| AOFF_GAP | - | Aspect offset gap? 0=no 1=gap |
| ASPTYPE | - | Solution method |
| COUNT_RATE | count/second | Count Rate |
HRC Dead Time Factor
| Filename | Description | Content | SDP Pipeline |
|---|---|---|---|
| hrc_dtf1.fits | HRC dead time factor | DTFSTATS | HRC1 |
Description:
The dead time correction factors as a function of time. For ACIS observations, the dead time correction is recorded in the DTCOR header keyword. Since the HRC dead time correction factor varies during the observation, however, the value of DTCOR represents an average and the individual values are stored in the dtf1.fits file.
Creator tool: hrc_calc_dead_time
DTF-specific columns:
| Column Name | Units |
|---|---|
| TIME | s |
| DTF | |
| DTF_ERR | |
| PROC_EVT_COUNT | count |
| TOTAL_EVT_COUNT | count |
| VALID_EVT_COUNT | count |
| STATUS |