KPL/IK GRNS Instrument Kernel =========================================================================== This instrument kernel (I-kernel) contains references to mounting alignment, operating modes, and timing as well as internal and FOV geometry for the Psyche Gamma Ray and Neutron Spectrometer (GRNS). Version and Date --------------------------------------------------------------------------- Version 0.4 -- August 29, 2025 -- Matt Barnes, NAIF/JPL Updated GRS/NS footprint description per [9] and [10]. Changed FOV definitions to use 36.86 half angle approximation per description of footprint approximation given in [10]. Version 0.3 -- April 26, 2021 -- Matt Barnes, NAIF/JPL Changed IDs to start with -255 instead of -69 to reflect PSYCH S/C ID change to -255, see [3] for details. Version 0.2 -- May 14, 2019 -- Boris Semenov, Masha Liukis, NAIF/JPL * Added new reference documents. * Updated FOV parameters (see [8]). Version 0.1 -- January 29, 2018 -- Boris Semenov, NAIF/JPL Preliminary version based on the mission proposal information; to be reviewed by the instrument team and updated based on their feedback. Updated some descriptions, diagrams, indentation, and paragraph wrapping. Renamed FOV sections to Footprint Intensity. Removed the Patform ID section. Added bogus FOVs intended for testing GRS and NS frames. Version 0.0 -- May 8, 2017 -- Masha Liukis, NAIF/JPL Preliminary version. References --------------------------------------------------------------------------- 1. ``Kernel Pool Required Reading'' 2. ``C-kernel Required Reading'' 3. Psyche Frames Definition Kernel (FK), latest version. 4. 02_Psyche_CSR_Redacted_Science.pdf. 5. Foldout G1. Flight System Overview. 6. The mapping and planetary spatial infrastructure team (MAPSIT): addressing strategic planning needs for planetary cartography, S. J. Lawrence et al., 2016 7. msgr_grns_v110.ti, the latest GRSNS IK from the MESSENGER SPICE PDS archive (MESS-E/V/H-SPICE-6-V1.0). 8. Psyche GRNS specifications. 9. Chabot, N.L., Peplowski, P.N., Ernst, C.M., Nair, H., Lucks, M., Steele, R.J. and Lawrence, D.J., 2021. MEGANE investigations of Phobos and the small body mapping tool. Earth, Planets and Space, 73(1), p.217. 10. Lawrence, D.J., Elphic, R.C., Feldman, W.C., Prettyman, T.H., Gasnault, O. and Maurice, S., 2003. Small-area thorium features on the lunar surface. Journal of Geophysical Research: Planets, 108(E9). https://doi.org/10.1029/2003JE002050 Contact Information --------------------------------------------------------------------------- Matt Barnes, NAIF/JPL, (818) 354-5942, matthew.j.barnes@jpl.nasa.gov Implementation Notes --------------------------------------------------------------------------- Applications that need SPICE I-kernel data must ``load'' the I-kernel file, normally during program initialization. Loading the kernel using the SPICELIB routine FURNSH causes the data items and their associated values present in the kernel to become associated with a data structure called the ``kernel pool''. The application program may then obtain the value(s) for any IK data item using the SPICELIB routines GDPOOL, GIPOOL, GCPOOL. Routine GETFOV may be used if the file contains instrument field-of-view (FOV) specification. See [1] for details. This file was created with, and can be updated with a text editor or word processor. Conventions for Specifying Data --------------------------------------------------------------------------- Data items are specified using ``keyword=value'' assignments [1]. All keywords referencing values in this I-kernel start with the characters `INS' followed by the NAIF Psyche instrument ID code, constructed using the spacecraft ID number (-255) followed by the NAIF three digit ID number for GRNS module. These IDs are defined in [4] as follows: Instrument name ID -------------------- ------- PSYC_GRS -255150 PSYC_NS -255160 The remainder of the keyword is an underscore character followed by the unique name of the data item. For example, the GRS boresight direction in the GRS frame is specified by INS-255150_BORESIGHT The upper bound on the length of all keywords is 32 characters. If a keyword is included in more than one file, or if the same keyword appears more than once within a single file, the last assignment supersedes any earlier assignments. Overview --------------------------------------------------------------------------- From [4]: The Gamma-Ray and Neutron Spectrometer (GRNS) provides elemental composition measurements at Psyche, especially the concentration of iron, nickel, silicon, and potassium. It is based on the successful MESSENGER GRNS and Van Allen Probes RBSPICE and is built by the same engineering team. The GRNS has large margin for the direct gamma-ray Ni measurement, and provides for an independent and complementary neutron-based measurement of Psyche's Ni abundance. The instrument combines high-heritage sensors with updated versions of latest spaceflight-proven electronics, and incorporates improvements based on lessons learned from the MESSENGER GRS. The Neutron Spectrometer (NS) measurements provide an independent measure of the metal-to-silicate and relative Ni variability across Psyche's surface [6]. Specifically, the GRNS measures neutrons with four neutron energy (En) band-pass filters. The energy ranges are slow (0.04 eV500 keV). The slow-neutron range provides unique information about the lowest energy thermal neutrons; low-energy epithermal neutrons provide information about H variations; the sensitivity of shield neutrons is biased to the highest energy epithermal neutrons, which provides information about Ni abundances [6]; fast neutrons provide a measure of average atomic mass [Gasnault et al., 2001]. The GRNS consists of two separate subsystems: A. Gamma-Ray Spectrometer (GRS); B. GRS Data Processing Unit (DPU); C. Neutron Spectrometer (NS); D. NS DPU. The GRS is functionally identical to that used on MESSENGER. The neutron spectrometer (NS) sensors are identical to those used on Lunar Prospector. The electronics are functionally identical to the MESSENGER electronics and are separated into two boxes. The heart of the GRS is a coaxial high-purity germanium (HPGe) crystal cryocooled to 90 K. The detector is the identical size and shape used in the MESSENGER GRS. The HPGe is thermally isolated from its surroundings by a harness of Kevlar strings within a vacuum cryostat. Based on a trade study carried out in Phase A, the GRS uses a long-life pulse-tube microcryocooler. This cooler is low mass (450 g), exceeds all mission lifetime requirements, and poses negligible magnetic contamination. GRS/NS Footprint Intensity --------------------------------------------------------------------------- GRS and NS are omni-directional sensors that detect events from all possible directions. Accordingly, the GRS and NS require no SPICE FOV cutoff. When in orbit of asteroid Psyche, the footprint of a given measurement is derived from the altitude of the spacecraft, the asteroid shape, and the instrument orientation as detailed in [9]. In this observation geometry, the GRS or NS boresight is defined by a vector from the S/C centerline to the subsatellite point, and the full-width at half-maximum (FWHM) of this footprint on the surface can be approximated as 1.5 times the orbital altitude of the respective observation [10]. Note that the actual footprint and intensity as used for science analysis will be calculated following the procedure outlined in [9]. GRS and NS FOVs --------------------------------------------------------------------------- Given the above description of the GRS and NS footprint, and in particular the statement: " the full-width at half-maximum (FWHM) of this footprint on the surface can be approximated as 1.5 times the orbital altitude of the respective observation " FOVs providing this approximate footprint are provided below. These FOVs are defined as circular with a half width defined by a right triangle which has an opposite side 0.75 times the length of the near side, giving a half angle of 36.86 degrees: ___ _-| ^ _-' | | _-' | o | _-' 36.86 | S/C x--------------> 1.5 `~_ | to | `~_ | Psyche | `~_ | | `~| V --- |<-- 1.0 -->| Plane X = 0 The FOVs defined below put the boresight of the FOV along the instrument +Z axis for backward compatibility. Note that this will only point toward Psyche if the S/C -X axis is pointed at Psyche. \begindata INS-255150_FOV_FRAME = 'PSYC_GRS' INS-255150_FOV_SHAPE = 'CIRCLE' INS-255150_BORESIGHT = ( 0.0, 0.0, 1.0 ) INS-255150_FOV_CLASS_SPEC = 'ANGLES' INS-255150_FOV_REF_VECTOR = ( 0.0, 1.0, 0.0 ) INS-255150_FOV_REF_ANGLE = ( 36.86 ) INS-255150_FOV_ANGLE_UNITS = 'DEGREES' INS-255160_FOV_FRAME = 'PSYC_NS' INS-255160_FOV_SHAPE = 'CIRCLE' INS-255160_BORESIGHT = ( 0.0, 0.0, 1.0 ) INS-255160_FOV_CLASS_SPEC = 'ANGLES' INS-255160_FOV_REF_VECTOR = ( 0.0, 1.0, 0.0 ) INS-255160_FOV_REF_ANGLE = ( 36.86 ) INS-255160_FOV_ANGLE_UNITS = 'DEGREES' \begintext End of IK file.