uvotattcorr - adjust attitude file with information from UVOT aspect corrections


uvotattcorr attfile=<filename> corrfile=<filename> outfile=<filename>


The Swift spacecraft attitude is available from several sources in the telemetry. Attitude knowledge onboard is not as fine as what can be obtained from comparing positions of stars in UVOT images to catalog positions. In addition, when the spacecraft transitions between slewing and pointed observations, the source of attitude information shifts from coarse to fine, resulting in a noticeable jump in the earliest exposures found in particular in GRB AT sequences. The purpose of uvotattcorr is to take the refined position information obtained from 'uvotskycorr' and apply it to the available spacecraft attitude information (which is 'atjumpcorr'ed in the pipeline), creating a more accurate attitude file.

The pipeline attempts to find an aspect solution for each image in a UVOT observing sequence. The results of these corrections can then applied to the existing attitude file. Since a sequence can contain gaps between images (and thus aspect solutions), and the exposure times can vary from tens of seconds to thousands of seconds, the offsets are first interpolated before being applied to the existing attitude. Corrections are considered valid for the snapshot in which they occur. During a snapshot which has no aspect corrections, no change is made to the attitude. Otherwise, the correction at a given time is found by linearly interpolating between (or extrapolating) the nearest known correction(s).

The solutions to the aspect corrections are found in the housekeeping file sw* At present, the pipeline creates a new corrected attitude file, sw*uat.fits, when uvotattcorr is run.


attfile [filename]
Swift attitude file (normally sw<obsid>sat.fits).

corrfile [filename]
UVOT aspect corrections file (normally sw<obsid>

outfile [filename]
Attitude file corrected for UVOT.

(deltafile = NONE) [filename]
Delta attitude file. The special value NONE indicates to not create this output.

(chatter = 3) [integer] <1-5>
Standard HEAdas chatter parameter.


The following examples illustrate running uvotattcorr

1. run uvotattcorr on a given attitude and corrections file

      uvotattcorr attfile=sw12345678012sat.fits \


uvotskycorr, uvotaspcorr, attjumpcorr


June 2007