Good Time Intervals (GTI)
and the Mission Timeline (MTL)
| Level | Instrum | Data product | Content | Pipeline | Filename template |
|---|---|---|---|---|---|
| L1 | ACIS | ACIS Good Time Interval | GTI | ACIS1 | flt1.fits |
| L1 | ACIS | ACIS Mission Timeline | MTL | ACIS1 | mtl1.fits |
| L1 | HRC | HRC Good Time Interval | GTI | HRC1 | std_flt1.fits |
| L1 | HRC | HRC Mission Timeline | MTL | HRC1 | mtl1.fits |
ACIS Good Time Interval (GTI)
| Level | Instrum | Data product | Content | Pipeline | Filename template |
|---|---|---|---|---|---|
| L1 | ACIS | ACIS Good Time Interval | GTI | ACIS1 | flt1.fits |
description:
This 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", between TSTART and TSTOP, are periods when observing conditions were good. The two principal causes of 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. See the CIAO threads page for more information.
file name:
GTI information is typically contained in the MTL or event files. It is not distributed as an independent data product. Look for GTI blocks (one per chip) in files whose names contain: 'evt', 'mtl1', 'img2', or 'flt1'.
creator pipeline:
ACIS L1
creator tool:
dmgti - GTIs are built on a 'per chip' basis. The GTI blocks are then attached to certain other data products, as noted above.
useful links:
- GTI entry in the CIAO Dictionary.
GTI specific columns:
| Column Name | Units | Description |
|---|---|---|
| START | seconds | Good time interval start time |
| STOP | seconds | Good time interval stoptime |
ACIS Mission Timeline (MTL)
| Level | Instrum | Data product | Content | Pipeline | Filename template |
|---|---|---|---|---|---|
| L1 | ACIS | ACIS Mission Timeline | MTL | ACIS1 | mtl1.fits |
description:
This file contains the telescope's housekeeping and configuration information. 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 part) to create the GTIs.
Important parameters include: pointing relative to the sun's limb, particle flux, aspection solution status, grating position, etc.
file name:
*_mtl1.fits
creator pipeline:
acis_L1
creator tool:
mtl_build_table
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 |
| 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 | - | - |
| EVTSENT | - | - |
| DETNAM | - | - |
| DATAMODE | - | - |
| READMODE | - | - |
| FP_TEMP | - | - |
| GRATING | - | - |
HRC Good Time Interval (GTI)
| Level | Instrum | Data product | Content | Pipeline | Filename template |
|---|---|---|---|---|---|
| L1 | HRC | HRC Good Time Interval | GTI | HRC1 | std_flt1.fits |
For more detailed information, see the ACIS GTI section.
creator pipeline:
HRC L1
creator tool:
dmgti - GTIs are built on a 'per chip' basis. The GTI blocks are then attached to certain other data products, noted above.
GTI specific columns:
| Column Name | Units | Description |
|---|---|---|
| START | seconds | Good time interval start time |
| STOP | seconds | Good time interval stoptime |
HRC Mission Timeline (MTL)
| Level | Instrum | Data product | Content | Pipeline | Filename template |
|---|---|---|---|---|---|
| L1 | HRC | HRC Mission Timeline | MTL | HRC1 | mtl1.fits |
For more detailed information, see the ACIS MTL section.
description:
The HRC MTL file contains nearly identical information to the ACIS MTL file. HRC-specific parameters include: voltage monitors and image diagnostics.
file name:
*_mtl1.fits
creator pipeline:
HRC L1
creator tool:
mtl_build_table
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 | - | Imaging Bot MCP HV Monitor |
| IMHBLV | - | Imaging Bot & TOP MCP HV Monitor |
| SPHVLV | - | Spect Bot MCP HV Monitor |
| SPHBLV | - | 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 | - |
| GRATING | - | - |
| DETNAM | - | HRC detector name |
| DET_HV | - | High Voltage ON or OFF |
| DATAMODE | - | - |
| MOVING | - | - |
| STATUS | - | - |
| DTF | - | - |
| AOFF_GAP | - | Aspect offset gap? 0=no 1=gap |
| ASPTYPE | - | Solution method |
| RATE | count/second | Count Rate |
