Acquisition star statistics

The mica.stats.acq_stats module includes code to gather acquisition star statistics data for each observation and return those data to the user.

To get the whole acquisition table data:

>>> from mica.stats.acq_stats import get_stats
>>> stats = get_stats()
>>> stats[(stats['obsid'] == 5438) & (stats['slot'] == 1)][0]['dy']
8.4296239297976854

The hdf5 in-kernel searches may be faster working with the table directly for some operations.

Data table fields

The acquisition statistics data table contains the following columns:

Column	Description
obsid	obsid
obi	observation interval number
acq_start	acquisition datestart from kadi event
guide_start	guide transition datestart from kadi event
guide_tstart	guide transition start from kadi event in Chandra secs
one_shot_length	one shot delta quaternion arc length for this obsid manvr (arcsec)
revision	revision string representing the software version
slot	ACA readout slot id
idx	starcheck star catalog index id
type	star catalog type (BOT or ACQ)
yang	commanded y-angle position for center of readout window (arcsec)
zang	commanded z-angle position for center of readout window (arcsec)
halfw	acquisition search box half width (arcsec)
mag	catalog MAG_ACA of acquisition star
acqid	acquisition success indicator (boolean)
star_tracked	something tracked within 5 arcsecs during acq interval (boolean)
spoiler_tracked	something tracked outside 5 arcsecs during acq interval (boolean)
img_func	image status at transition: can be ‘NONE’, ‘star’, ‘spoiler’, ‘RACQ’, ‘SRCH’
n_trak_interv	number of intervals during acq when something was tracked
max_trak_cdy	max “corrected” delta-y during acquisition (arcsec)
mean_trak_cdy	mean “corrected” delta-y during acquisition (arcsec)
min_trak_cdy	min “corrected” delta-y during acquisition (arcsec)
max_trak_cdz	max “corrected” delta-z during acquisition (arcsec)
mean_trak_cdy	mean “corrected” delta-z during acquisition (arcsec)
min_trak_cdz	min “corrected” delta-z during acquisition (arcsec)
max_trak_mag	max observed magnitude during acquisition
mean_trak_mag	mean observed magnitude during acquisition
min_trak_mag	min observed magnitude during acquisition
cdy	“corrected” (see below) delta-y at guide transition. (arcsec)
cdy	“corrected” (see below) delta-z at guide transition (arcsec)
dy	delta-y at guide transition. expected position (see below) determined using onboard est. attitude (arcsec)
dz	delta-z at guide transition. expected position (see below) determined using onboard est. attitude (arcsec)
ion_rad	ionizing radiation flag set at transition (boolean)
def_pixel	defective pixel flag set at transition (boolean)
mult_star	multiple star flag set at transition (boolean)
sat_pix	saturated pixel flag set at transition (boolean)
mag_obs	observed magnitude at transition
yang_obs	observed y-angle at transition (arcsec)
zang_obs	observed z-angle at transition (arcsec)
agasc_id	AGASC (catalog) id
color1	AGASC COLOR1, estimated B-V color
ra	AGASC right ascension (degrees)
dec	AGASC declination (degrees)
epoch	AGASC EPOCH
pm_ra	AGASC PM_RA, proper motion in ra (milli-arcsec/year)
pm_dec	AGASC PM_DEC, proper motion in dec (milli-arsec/year)
var	AGASC VAR, known or suspected variable star
pos_err	AGASC POS_ERR, position error (milli-arcsec)
mag_aca	AGASC MAG_ACA, ACA mag
mag_err	AGASC MAG_ERR, (to be fixed, this should have been MAG_ACA_ERR)
mag_band	AGASC MAG_BAND, integer code for spectral band
pos_catid	AGASC POS_CATID, integer code for position catalog
aspq1	AGASC ASPQ1, integer spoiler code
aspq2	AGASC ASPQ2, integer proper motion flag
aspq3	AGASC ASPQ3, integer dist in 100m-arcsec to nearest Tycho2 star
acqq1	AGASC ACQQ1, mag diff to brightest star within 53.3” (0.01mags)
acqq2	AGASC ACQQ2, mag diff to brightest star within 107” (0.01mags)
acqq4	AGASC ACQQ4, mag diff to brightest star within 267.5” (0.01mags)
n100_warm_frac	estimated n100 fraction of CCD pixels for this observation
ccd_temp	mean CCD temperature over 500 seconds surrounding guide transition
known_bad	ignore this star in standard processing (boolean)
bad_comment	reason to ignore a “known_bad” star

Note that dy/dz are observed yag/zag (t_guide) - predicted yag/zag (t_guide) using AOATTQT (estimated attitude). Observed yag/zag are from AOAC{Y,Z}AN, and t_guide is the time of the first sample with AOACASEQ = ‘GUID’. t_guide is the same as manvrs.guide_start in kadi. The one-shot attitude update occurs in telemetry on the sample after the GUID transition. In particular, dy/dz are used in the check for wrong box acquisition anomaly as the the estimated attitude for dy/dz gives a reasonable approximation of the OBC estimated attitude at the time of commanding the search boxes. (though the estimated attitude at t_acq would be even better for that)

For the columns that reference “corrected” y-angle and z-angle, cdy/cdz, these are the observed yag/zag (t_guide) - predicted yag/zag (t_guide) using the estimated attitude at that time transformed/corrected by the one-shot quaternion (which is actually calculated from the next one or two samples).

Processing

For each observation, after the observation has run and telemetry is available, the acquisition and guide stats process does the following:

• Fetches the AGASC information for each star in the catalog

• Fetches the PCAD data at the end of the acquisition interval

• For each acquisition star determines:

  • If that star was “successfully” acquired

  • What the observed magnitude and position of the star were in the last PCAD telemetry readout before the guide transition.