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SWIFTTDRSS - Swift TDRSS Messages

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Overview

This database table is derived from the Swift TDRSS messages sent on ground soon after a BAT trigger occurs on-board. For each trigger there are associated up to 14 messages, however not all are always generated and sent on ground. The messages are generated on board by the BAT, XRT and UVOT instruments and the Figure of Merit part of the observatory's autonomy. The BAT and XRT can each have five different message types. The UVOT and FOM can each have two different message types. These TDRSS messages are the results of the on-board data processing of the three instruments and some contain data products. They are first distributed via the GCN and later archived. The BAT messages are: alert, 'ack' containing the position, or 'nack' if the position could not be calculated, a lightcurve and scaled map. The XRT messages are: centroid containing the position, an image (if the position has been calculated), centroid error if the position could not be calculated, spectra in Low Rate Photodiode and Windowed Timing modes, a lightcurve. The UVOT messages are: finding chart containing star positions and a subimage centered on the XRT position. The FOM messages are used to indicate if the FOM will or will not observe the new target and if the spacecraft will (or will not) request a slew for the new target.

The parameters in this database table are a collection of high level information taken from the following messages : the BAT alert, 'ack' or 'nack' message, the FOM messages, the XRT position and image. If the information is not available the fields are left blank. All messages are provided as data products within this database table.


Bulletin

The SWIFTTDRSS database table was last updated on 23 July 2014.

Provenance

This database table is generated at the Swift processing site. During operation, it is updated on daily basis.

Parameters

Target_ID
This is the trigger number assigned on board (BAT GRB alert message). The numerical value can include up to 8 digits (e.g. do not include leading zeros).

Obs_Segment
Observation Segment. The Swift observation strategy is similar to a monitoring campaign in which a target is observed several times. This parameter, corresponds to the number of times a specific target has been observed, and it is assigned a value of 0 to the first observation of that target. Since the TDRSS messages are part of the first observation in response to a trigger, it is expected that this value will be typically zero.

ObsID
Unique Observation Number (Target_ID + Obs_Segment). This parameter contains a numeric value that uniquely identifies an observation. This value is the combination of the numerical value assigned to a target and the observation segment and is derived from the parameters target_id and obs_segment. The numerical value is a fixed 11-digit number, where the first 8 are for the target and last 3 are for the observation segment.

RA
This is the trigger Right Ascension. If the XRT centroid message is available, it is populated by the XRT position. If the XRT is not available, it is populated by the BAT position as reported in the 'ack' message. If the BAT ack message is also not available, the field is left empty.

Dec
This is the trigger Declination. If the XRT centroid message is available, it is populated by the XRT position. If the XRT is not available, it is populated by the BAT position as reported in the ack message. If the BAT ack message is also not available, the field is left empty.

Pos_Flag
Flag to indicate from where the position is taken. The possible values are: 1=BAT, 2=XRT, 0=neither available.

Time
Time of the Trigger taken from the BAT alert message. The time is corrected to the UTC system.

Time_Seconds
Time of the Trigger in seconds taken from the BAT alert. This is the time of the trigger measured in the mission elapsed time and no correction is applied to UTC

Ucft_Corr
This is the UTCF Correction (in seconds) taken from the BAT alert. If applied to the time_seconds, the resulting time is in UTC.

Trigger_Satisfied
The table index of the trigger that had the highest significance level of all those satisfied. The value is taken from the BAT alert message.

Rate_Score
Rate Score associated with the trigger taken from the BAT alert message.

Rate_Score_SNR
Rate Score signal-to-noise significance of the trigger taken from the BAT alert message.

BAT_RA
BAT Right Ascension. Taken from the BAT position ack message.

BAT_Dec
BAT Declination. Taken from the BAT position ack message.

Time1
Time of the Trigger taken from the ack (or nack) message. This value can be different from that reported in the alert, because it is based on a different on-board analysis.

Time_Seconds1
Time of the Trigger in seconds taken from the BAT ack message (or nack). This is the time of the trigger measured as in the mission elapsed time and no correction is applied to UTC. This value can be different from that reported in the alert, because it is based on a different on-board analysis.

Trigger_Satisfied1
The table index of the trigger that had the highest significance level of all those satisfied. The value is taken from the BAT ack message (or nack). This value can be different from that reported in the alert because, based it is on a different on-board analysis

Rate_Score1
Rate Score to the trigger taken from the BAT ack message(or nack). This value can be different from that reported in the alert, because it is based on a different on-board analysis

Rate_Score_SNR1
Rate Score signal-to-noise significance of the trigger taken from the BAT ack (or nack) message.This value can be different from that reported in the alert, because it is based on a different on-board analysis.

Image_Trigger
Flag to indicate that the trigger was detected in the on-board image analysis. Taken from the ack (or nack) message.

Catalog_Source
Flag to indicate that the source was part (or not) of the on-board BAT Catalog. Taken from the ack (or nack) message.

Source_Interesting
Flag to indicate if the source is interesting. Taken from the ack (or nack) message.

Point_Source
Flag to indicate if the source is a point source within the BAT. Taken from the ack (or nack) message.

Source_Is_GRB
Flag to indicate if the source could be a Gamma-Ray Burst. Taken from the ack (or nack) message.

BAT_Phi
BAT Phi Angle. Distance from the target (trigger) from the BAT boresight given in degrees. Values range from 0-180 degrees. Taken from the ack (or nack) message.

BAT_Theta
BAT Theta Angle. Angle of the target (trigger) about BAT boresight given in degrees. Values range from 0-360 degress. If set to 0 is in the spacecraft +Y direction if set to 90 is in the spacecraft -Z direction. Taken from the ack (or nack) message.

BAT_Peak_Rate
BAT peak count rate observed during a time interval the value of which is stored in the source_exposure parameter. Taken from the ack (or nack) message.

BAT_Tot_Counts
BAT total counts on source (not background subtracted) observed during an exposure time the value of which is stored in the source_exposure parameter. Taken from the ack (or nack) message.

BAT_Back_Counts
BAT background counts observed during an exposure time the value of which is stored in the back_exposure parameter. Taken from the ack (or nack) message.

BAT_Net_Counts
BAT background subtracted counts observed during a time interval the value of which is stored in the source_exposure parameter. Taken from the ack (or nack) message.

BAT_Trigger_Stop
BAT Trigger stop time. The time of the trigger and the stop time of the trigger define the time interval used to calculate the total counts, and the peak rate. Taken from the ack (or nack) message.

Image_Significance
The BAT image detection significance of the trigger provided by the on-board analysis. Taken from the ack (or nack) message.

Source_Exposure
The BAT effective exposure on source. Taken from the ack (or nack) message.

Back_Exposure
The BAT effective exposure on background. Taken from the ack (or nack) message.

New_AT
Flag to indicate if the new trigger has sufficient merit to become the next automatic target (AT). Taken from the FOM 'will/will not observe' message.

FOM_Observe
Flag to indicate that the new trigger has sufficient merit to warrant requesting a slew. Taken from the FOM 'will/will not observe' message.

Merit
Record the merit value associate to the new trigger. Taken from the FOM 'will/will not observe' message.

PNT_RA
Right Ascension of the trigger as listed in the FOM spacecraft 'will/will not slew' message. This value is used to re-point the satellite

PNT_Dec
Declination of the trigger as listed in the FOM spacecraft 'will/will not slew' message.This value is used to re-point the satellite

PNT_Roll
Predicted roll angle that will be achieved if the satellite is re-pointed at the trigger position. Taken from the FOM spacecraft 'will/will not slew' message.

SC_Observe
Flag to indicate if the spacecraft will or will slew to the position of the new trigger. The values are set as follows: 0=will slew, Non-zero=will not slew. Taken from the FOM spacecraft 'will/will not slew' message.

Wait_Time
Number of seconds to wait before the new target is visible. Taken from the FOM spacecraft 'will/will not slew' message.

Wait_Constraint
Number of seconds that the target can be observed before constraint violation. Taken from the FOM spacecraft 'will/will not slew' message.

XRT_RA
XRT Right Ascension of the trigger. The XRT position is calculated on board and this value is taken from the XRT position message.

XRT_Dec
XRT Declination of the trigger. The XRT position is calculated on board and this value is taken from the XRT position message.

Rate_DN
XRT Rate measured on board. This value is taken from the XRT position message and corresponds to the total charge recorded in the subimage (51x51) of the XRT centered on the trigger position.

XRT_Time
Start time of the XRT integration used to determine the position. Calculated from the seconds, subseconds, and UTCF fields in the XRT position message.

XRT_Flux
The XRT flux (ergs/cm^2/s) obtained by converting the rate calculated on ground and stored in the parameter rate_dn1. The flux conversion is obtained assuming Crab spectral parameters. Taken from the XRT image message after ground processing.

Rate_DN1
The XRT rate measured on ground using all change values bias subtracted in the image 51x51 pixels. The rate is divided by the exposure stored in the parameter xrt_exposure. The rate is taken from the XRT image message after ground processing.

XRT_Exposure
XRT exposure given in second of the image message. Taken from the XRT image message after ground processing.

XRT_Pos_Err
XRT position error in arcminutes calculated on ground. Taken from the XRT image message after ground processing.

XRT_DN
XRT total charge bias subtracted recorded in the 51x51 image. Taken from the XRT image message after ground processing.

Processing_Date
This records the date when the data where processed. If a data set has been processed more than one time, it reports the date of the last processing.

Processing_Version
This records the version of the processing script used in the pipeline to derive the data from these messages.

Num_Processed
This records the number of times a data set has been processed using the same processing version of the script.

Master_Flag
This flag is set to Y if there is an observation associated with the TDRSS message.

LII
This is the trigger Galactic Longitude. If the XRT centroid message is available, it is populated by the XRT position. If the XRT is not available, it is populated by the BAT position as reported in the 'ack' message. If the BAT ack message is also not available, the field is left empty.

BII
This is the trigger Galactic Latitude. If the XRT centroid message is available, it is populated by the XRT position. If the XRT is not available, it is populated by the BAT position as reported in the ack message. If the BAT ack message is also not available, the field is left empty.


Contact Person

Questions regarding the SWIFTTDRSS database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 12-Sep-2008