urn:nasa:pds:kaguya_grs_spectra:data_ephemerides:kgrs_ephemerides 1.0 1.11.0.0 Product_Observational 2019-09-30 1.0 First release. 2007-12-14T04:15:35Z 2009-05-28T07:43:22Z Science Derived This document describes the methods used to calculate ephemerides, pointing, and geometry (EPG) data that accompany gamma-ray spectra acquired by the JAXA/SELENE (Kaguya) mission to the Moon. The data are part of the Kaguya gamma-ray spectrometer (KGRS) calibrated spectra archived at the Planetary Data System’s Geosciences Node. The EPG data file includes the position and orientation of the spacecraft in a fixed lunar reference frame along with the solid angle subtended by the Moon. The EPG data are needed for the following analysis tasks: selection of valid data (e.g. entries that meet pointing and altitude criteria), geometry/altitude corrections, and mapping. The methods used to determine the parameters recorded in the data set are described here. The energy-dependent, efficiency-area product of KGRS accompanies the EPG data in the label file. A description of the methods used to calculate the efficiency-area product and experimental validation is described. Kaguya Mission urn:nasa:pds:context:investigation:mission.kaguya data_to_investigation Kaguya Kaguya Spacecraft urn:nasa:pds:context:instrument_host:spacecraft.kaguya is_instrument_host GRS Instrument urn:nasa:pds:context:instrument:kaguya.grs is_instrument Moon Satellite urn:nasa:pds:context:target:satellite.earth.moon collection_to_target urn:nasa:pds:kaguya_grs_spectra:document:kgrs_ephemerides_doc data_to_document kgrs_ephemerides.csv 2019-08-22T00:00:00Z 0 PDS DSV 1 This archive consists of three spectrum files (each corresponding to one KGRS epoch) and one unified EPG file. The spectrum files contain a time series of corrected and calibrated pulse height spectra acquired by KGRS's HPGe detector in the lunar orbit. In the spectrum files, each row contains the spacecraft clock (sclk) ticks and UTC time corresponding to the end of the accumulation interval (17 s), with the two sets of the 8192-channel HPGe spectra accumulated. In the EPG file, each row starts with sclk recorded at the end of the accumulation interval to match spacecraft positions, pointing, and correction factors with the corrected spectra. Note that the UTC time and ephemeris time included in the EPG file correspond to the midpoint of the accumulation interval. 1333699 Carriage-Return Line-Feed Comma 11 3 sclk 1 ASCII_Integer seconds Spacecraft clock (sclk) ticks at the end of the accumulation interval in seconds. The origin of the sclk is Jan 6, 1980, 0:0:0. Each spectrum, scaler value, and ephemeris have a unique sclk value, which can be used as an identifier. Kaguya's sclk is also known as a time index (TI). utc_mid 2 ASCII_String UTC time at the midpoint of the accumulation interval in seconds et_mid 3 ASCII_Real seconds Ephemeris time at the midpoint of the accumulation interval in seconds 1 3 1 0 position 1 ASCII_Real kilometers Spacecraft position (x, y, z) in km at the midpoint epoch time for each measurement in the Mean Earth/Polar Axis (ME) fixed lunar reference frame body_center_distance 4 ASCII_Real kilometers Distance from the spacecraft to body center in km latitude 5 ASCII_Real degrees Spacecraft latitude in degrees at the midpoint epoch time for each measurement longitude 6 ASCII_Real degrees Spacecraft longitude in degrees at the midpoint epoch time for each measurement subsatellite_distance 7 ASCII_Real kilometers Distance in km from the spacecraft to the shape model in the direction of body center equivalent_altitude 8 ASCII_Real kilometers Equivalent altitude of the spacecraft in km for a sphere of the same volume as the Moon (with a radius, R of 1737.4 km) that gives the same SOLID_ANGLE as determined from the shape model: EQUIVALENT_ALTITUDE = R ( 1/ sqrt{ 1 - [ 1 - SOLID_ANGLE/(2*PI) ]^2} - 1) solid_angle 9 ASCII_Real steradian Solid angle in sr subtended by the shape model at the spacecraft solid_angle_uncertainty 10 ASCII_Real steradian Monte Carlo statistical uncertainty in SOLID_ANGLE in sr solid_angle_reference 11 ASCII_Real steradian Solid angle in sr subtended by the reference sphere (with a radius of 1737.4 km) at the spacecraft 2 3 1 0 pointing 1 ASCII_Real degrees Cosines of the angles between the direction to body center in the instrument fixed frame and the x-, y-, and z-axes of the instrument coordinate system 3 5 1 0 instrument_response_function 1 ASCII_Real Coefficients for efficiency-area product (epsilon-A, in cm2), which is expressed as log(epsilon-A) = sum( c[i] x {log(E)}^i ), where i is the order of the fitted polynomial (0-4) and photon energy (E) has units of MeV.