Ancillary Engineering Data Files

Purpose

Ancillary engineering data is a subset of the engineering telemetry collected by the spacecraft that may prove useful for certain science data analyses. There is one ancillary engineering data file per long-cadence data collection interval. In some cases ancillary engineering data exists for time intervals where no valid science data was collected.

Data Retrieval

Files can be retrieved using either the K2 FFI+ or the Kepler FFI+ search form by selecting archive class "ENG". The Kepler search form will return engineering files with a start date on or before May 11, 2013. The K2 form will return engineering files obtained after 2013. The file names shown in the search results have the form "kplr[timestamp]" where the timestamp is the UTC time associated with the end of the corresponding long cadence file data in YYYYDDDHHMMSS format. The full name of the retrieved files will be in the form kplr[timestamp]_anc-eng.fits.

Since launch, over 93,000 engineering files have been archived and made public.

Composition

The ancillary engineering data files are in FITS format. Values for each mnemonic are contained in an individual FITS binary table extension containing 1 or more rows of 2 columns; one for the readout time (in MJD) and the other for the parameter value. The keywords in each extension give a rough description of the parameter. These files have roughly 200 extensions.

The ancillary engineering data headers are specified below.

FITS header keywords

Kepler Ancillary Engineering data header format:
keyword = value comment datatype option_flag
where 'value' is only shown for keywords with constant values,
and option_flag has values: Y = optional; N = required; C = constant

SIMPLE = T data conform to FITS standard L1 C
BITPIX = 0 bits per data value I2 N
NAXIS = 0 number of data array dimensions I2 N
EXTEND = T File may contain standard extensions L1 N
NEXTEND = Number of standard extensions I2 N
TELESCOP= Kepler telescope used to acquire data C06 C
INSTRUME= CCD identifier for instrument used to acquire data C03 N
RADECSYS= ICRS refernce frame of coordinates C4 C
DATE = date this file was written (yyyy-mm-dd) C10 N
ORIGIN = STScI institution responsible for creating FITS file C18 N
FILENAME= name of file C39 N
DATSETNM= data set name of the file C34 N
/ Configuration identifiers
FLSW_VER= Flight Software version number C20 N
SCCONFIG= Spacecraft configuration counter C20 N
/ Pointing information
RA-XAXIS= s/c -x axis Right Ascension (deg.) R4 N
DEC-XAXS= s/c -x axis declination (deg.) R4 N
ROLLANGL= s/c roll angle (deg. from N.) R4 N
END


XTENSION= BINTABLE extension type C08 N
BITPIX = bits per data value I2 N
NAXIS = 2 number of data array dimensions I2 N
NAXIS1 = length of first data axis I4 Y
NAXIS2 = length of second data axis I4 Y
PCOUNT = 0 number of parameter bytes following data table I2 C
GCOUNT = 1 number of groups I2 C
TFIELDS = number of fields in each table row I2 Y
INHERIT = T inherit the primary header L1 C
EXTNAME = extension name C08 N
EXTVER = extension version number I2 N
/ Ancillary Engineering Parameter Attributes
MNEMONIC= Mnemonic of telemetry item C08 N
PARAM_ID= Numeric identifier for telemetry item I2 N
PARDESCR= Ancillary engineering parameter description C30 N
PARSAMPR= Parameter telemetry sample rate (seconds) R8 N
PAR_TYPE= Parameter type: analog (1) or discrete (2) I2 N
PARUNITS= Parameter units C18 N
APP_ID = Science data set flight segment application id I2 N
PKT_ID = Science data set flight segment packet id I2 N
PACKET = Flight segment packet location C20 N
BYTE_BIT= Flight segment byte:bit location C10 N
MODE2RAT= Mode 2 packet rate (seconds) I2 N
/ Ancillary Engineering Parameter Table Statistics
ENGSTART= Start time of parameter data in table (MJD) R8 N
ENGEND = End time of parameter data in table (MJD) R8 N
PARCOUNT= Number of samples I4 N
PARAVERG= Average value of mnemonic in table R8 N
PARSTDEV= Standard deviation of mnemonic values in table R8 N
PAR_MIN = Minimum value of parameter in table R8 N
PAR_MAX = Maximum value of parameter in table R8 N
/ Ancillary Engineering Parameter Table Definition
TTYPE1 = TIME Ancillary engineering parameter readout time C08 C
TFORM1 = 1D Data format for time: REAL*8 C08 C
TDISP1 = G20.14 Format in which time is displayed C08 C
TUNIT1 = MJD Units for time: Modified Julian Date C08 C
/discrete data formats
TTYPE2 = VALUE Parameter value at readout time C08 C
TFORM2 = 20A Data format for parameter value: CHARACTER C08 C
TDISP2 = A20 Format in which parameter value is displayed C08 C
END
/analog data formats
TTYPE2 = VALUE Parameter value at readout time C08 C
TFORM2 = 1D Data format for parameter value: REAL*8 C08 C
TDISP2 = G20.14 Format in which parameter value is displayed C08 C
END