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*apply_bary* - Applying Barycentric Corrections to QPOE times

The barycentric corrections computed in 8.7.1 are applied to the event times in a time-sorted QPOE file. In addition, the times are converted from spacecraft-clock units to UTC.

input files: rp90_sti.qp,

output files: rp90_out.qp

  ti> apply_bary

input qpoe file name: rp90_sti.qp[time=(1606720.0:1612809.8)]    # see Note 1&2
input correction table filename:
output qpoe file name: rp90_out
event definition: medium

SCC->UTC conversion table is calibrated to SCC 110883482.0000

first qpoe gti time   = J.D. 2448062.97604379,  SCC 1606720.00000000
last qpoe gti time    = J.D. 2448063.04652758,  SCC 1612809.80000000
first corr table time = J.D. 2448062.97569444
last corr table time  = J.D. 2448063.04652778

Barycenter Corrections applied to event times in rp90_out.qp
using correction table 
with reference position at RA =  22:08:41.60, DEC =  45:44:47.30
Creating QPOE output file: rp90_out.qp

NOTE: The output QPOE times are in seconds from noon of the MJD of the start of the first OBI.

To convert the times to MJD use the following formula:

MJDREFI + MJDREFF + (photon_time / 86400)

The values MJDREFI and MJDREFF can be found in the header of the output QPOE file. (MJDREFF should be 0.5)

NOTE 1: The orbit data records in the file are generated every 60 seconds during the observation. The apply_bary task calculates the barycenter timing corrections using a linear interpolation between the two orbit records for which an event time falls. Occasionally there is not a final orbit record, so that there may be events with arrival times occurring after the last orbit record. When calculating the barycenter timing corrections for these events, the apply_bary task uses a linear extrapolation from the previous two orbit records and gives the user a warning that an extrapolation is being used. This extrapolation should effect at most 60 seconds of data. The apply_bary task prints the times of the first and last event and the first and last orbit record, so that the user may assess the appropriateness of the extrapolation being performed.

For this dataset, there are 62 events that arrive up to $\sim$7 seconds after the last orbit record. The example above uses a time filter on the input qpoe file to filter out these events. The user may also use the qpcopy task to perform the filtering.

NOTE 2: The apply_bary task takes as input a time-sorted qpoe file, and allows the user to specify a region descriptor. There is a known bug when using large region descriptors with time-sorted qpoe files. The error usually manifests itself in the form of ``ERROR: PLIO: reference out of bounds on mask'' or ``ERROR: PLIO: stack overflow (plr_open)''. Since the standard qpoe file is spatially sorted, the user is encouraged to apply region descriptors when running the timsort task (as in example 8.3.1).

next up previous contents
Next: *scc_to_utc* - Converting Spacecraft Up: *calc_bary, apply_bary* - Barycentric Previous: *calc_bary* - Computing Barycentric