KPL/IK GALA Instrument Kernel =============================================================================== This instrument kernel (I-kernel) contains the GAnymede Laser Altimeter (GALA) transmitter and receiver parameters. Version and Date ------------------------------------------------------------------------------- Version 0.5 -- September 2, 2022 – Alexander Stark (GALA Team), DLR Marc Costa Sitja, ESAC/ESA Updated GALA instrument description and parameter table. Added two subsystems for the transmitter (main and redundant laser). Added detector parameters and corrected receiver FOV parameters. Version 0.4 -- June 30, 2022 -- Marc Costa Sitja, ESAC/ESA Corrected INS-28120_FOV_REF_ANGLE. Corrected F Number from F/1 to F/6. Version 0.3 -- June 04, 2016 -- Marc Costa Sitja, ESAC/ESA Updated all NAIF ID codes from -907* to -28* since the JUICE spacecraft NAIF ID has been updated from -907 to -28. Initial Release. Pending review by the GALA instrument team. Version 0.2 -- May 11, 2016 -- Jorge Diaz del Rio, ODC Space Corrected typos in text. Preliminary version. Pending review by the GALA instrument and JUICE Science Operations Working Group team. Version 0.1 -- January 31, 2016 -- Jorge Diaz del Rio, ODC Space Preliminary version. Pending review by the GALA instrument and JUICE Science Operations Working Group team. Version 0.0 -- July 24, 2013 -- Marc Costa Sitja, ISDEFE/ESA Initial Release. References ------------------------------------------------------------------------------- 1. ``Kernel Pool Required Reading'' 2. ``C-kernel Required Reading'' 3. JUICE Frames Definition Kernel (FK), latest version. 4. ``The Ganymede laser altimeter (GALA): key objectives, instrument design, and performance, Hussmann, H. et al. CEAS Space Journal 2019 Vol. 11 Issue 4, Pages 381-390, DOI: 10.1007/s12567-019-00282-8'' Contact Information ------------------------------------------------------------------------ If you have any questions regarding this file contact the ESA SPICE Service (ESS) at ESAC: Alfredo Escalante Lopez (+34) 91-8131-429 spice@sciops.esa.int or the JUICE Science Operations Center at ESAC: Marc Costa Sitja (+34) 91-8131-236 Marc.Costa@ext.esa.int Implementation Notes ------------------------------------------------------------------------------- Applications that need SPICE I-kernel data must ``load'' the I-kernel file, normally during program initialization. The SPICE routine FURNSH loads a kernel file into the pool as shown below. CALL FURNSH ( 'frame_kernel_name' ) -- FORTRAN furnsh_c ( "frame_kernel_name" ); -- C cspice_furnsh, frame_kernel_name -- IDL cspice_furnsh( 'frame_kernel_name' ) -- MATLAB 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''. Once the file has been loaded, the SPICE routine GETFOV (getfov_c in C, cspice_getfov in IDL and MATLAB) can be used to retrieve FOV parameters for a given instrument or structure. The application program may obtain the value(s) for any other IK data item using the SPICELIB routines GDPOOL, GIPOOL, GCPOOL (gdpool_c, gipool_c, gcpool_c in C, cspice_gdpool, cspice_gipool, cspice_gcpool in IDL and MATLAB). See [1] for details. This file was created with, and can be updated with a text editor or word processor. Naming Conventions and Conventions for Specifying Data ------------------------------------------------------------------------------- All names referencing values in this IK file start with the characters `INS' followed by the NAIF JUICE spacecraft ID number (-28) followed by a NAIF three-digit ID code for one of the GALA subsystem. This is the full list of names and IDs for the GALA subsystem described by this IK file: Name NAIF ID --------------------- --------- JUICE_GALA_RXT -28120 JUICE_GALA_TX_MAIN -28111 JUICE_GALA_TX_RED -28112 The remainder of the keyword name is an underscore character followed by the unique name of the data item. For example, the GALA Receiver Unit boresight direction in the JUICE_GALA_RXT frame is specified by: INS-28120_BORESIGHT The upper bound on the length of the name of any data item is 32 characters. If the same item is included in more than one file, or if the same item appears more than once within a single file, the latest value supersedes any earlier values. Instrument Description and Overview ------------------------------------------------------------------------------- From [4]: GALA’s main objective is to obtain topographic data of the icy satellites of Jupiter: Europa, Ganymede, and Callisto. By measuring the diurnal tidal deformation of Ganymede, which crucially depends on the decoupling of the surface ice layer from the deep interior by a liquid water ocean, GALA will obtain evidence for (or against) a subsurface ocean in a 500 km orbit around the satellite and will provide constraints on Ganymede’s ice shell thickness. In combination with other instruments, it will characterize the morphology of surface units on Ganymede, Europa, and Callisto providing not only topography but also surface roughness and albedo (at 1064 nm) measurements. GALA is a single-beam laser altimeter operating with up to 50 Hz (nominal 30 Hz) shot frequency at a wavelength of 1064 nm and pulse lengths of 5.5 ± 2.5 ns using a Nd:YAG laser. The return pulse is detected by an Avalanche Photo Diode (APD) with 100 MHz bandwidth and is digitized at a sampling rate of 200 MHz providing range measurements with a subsample resolution of 0.1 m and surface roughness measurements from pulse-shape analysis on the scale of the footprint size of about 50 m at 500 km altitude. The instrument is developed in collaboration of institutes and industry from Germany, Japan, Switzerland, and Spain. Table: GALA baseline instrument parameters ----------------------------------------------------------------------- Parameters Value Comments ----------------------------------------------------------------------- Pulse repetition rate 1 to 50 Hz variable ----------------------------------------------------------------------- Laser wavelength 1064.566 nm at 25° C ----------------------------------------------------------------------- Pulse Energy 17 mJ at 30 Hz 8 mJ at 50 Hz ----------------------------------------------------------------------- Pulse FWHM 5.18 ns at 30 Hz, main laser 8.44 ns at 50 Hz, main laser ----------------------------------------------------------------------- Beam divergence 100 mu rad full cone, main laser 100 mu rad full cone, red laser ----------------------------------------------------------------------- Spot size on the surface 50 m in 500km orbit ----------------------------------------------------------------------- Receiver telescope diameter 250 mm F/6 telescope ----------------------------------------------------------------------- Field of View (FOV) 580 mrad full cone ----------------------------------------------------------------------- Range resolution ~10 cm at optimal conditions ----------------------------------------------------------------------- Operation ranges < 3200 km technical limit (active mode) < 1600 km Europa < 1400 km Ganymede < 1100 km Callisto ----------------------------------------------------------------------- Mounting Alignment ------------------------------------------------------------------------------- Refer to the latest version of the JUICE Frames Definition Kernel (FK) [3] for the GALA reference frame definitions and mounting alignment information. GALA Laser Head and Transmitter Field of View Definitions ------------------------------------------------------------------------------- The GALA Transmitter Laser (TXL) beam can be produced by two lasers: main (MAIN) and redundant (RED). The laser beams from both have a divergence of 50 mu rad half-angle cone centered on the +Z axis of the JUICE_GALA_TXL_MAIN and JUICE_GALA_TXL_RED frame, respectively. This FOV definition corresponds to the NAIF Body Name: JUICE_GALA_TXL_MAIN. \begindata INS-28111_FOV_FRAME = 'JUICE_GALA_TXL_MAIN' INS-28111_FOV_SHAPE = 'CIRCLE' INS-28111_BORESIGHT = ( 0.000, 0.000, 1.000 ) INS-28111_FOV_CLASS_SPEC = 'ANGLES' INS-28111_FOV_REF_VECTOR = ( 0.000, 1.000, 0.000 ) INS-28111_FOV_REF_ANGLE = ( 0.00005 ) INS-28111_FOV_ANGLE_UNITS = 'RADIANS' \begintext This FOV definition corresponds to the NAIF Body Name: JUICE_GALA_TXL_RED. \begindata INS-28112_FOV_FRAME = 'JUICE_GALA_TXL_RED' INS-28112_FOV_SHAPE = 'CIRCLE' INS-28112_BORESIGHT = ( 0.000, 0.000, 1.000 ) INS-28112_FOV_CLASS_SPEC = 'ANGLES' INS-28112_FOV_REF_VECTOR = ( 0.000, 1.000, 0.000 ) INS-28112_FOV_REF_ANGLE = ( 0.00005 ) INS-28112_FOV_ANGLE_UNITS = 'RADIANS' \begintext GALA Receiver Telescope Field of View Definition ------------------------------------------------------------------------------- The GALA Receiver Telescope (RXT) Field of View (FOV) is defined as a 290 mu rad half-angle cone centered on the +Z axis of the JUICE_GALA_RXT frame. This FOV definition corresponds to the NAIF Body Name: JUICE_GALA_RXT. \begindata INS-28120_FOV_FRAME = 'JUICE_GALA_RXT' INS-28120_FOV_SHAPE = 'CIRCLE' INS-28120_BORESIGHT = ( 0.000, 0.000, 1.000 ) INS-28120_FOV_CLASS_SPEC = 'ANGLES' INS-28120_FOV_REF_VECTOR = ( 0.000, 1.000, 0.000 ) INS-28120_FOV_REF_ANGLE = ( 0.000290 ) INS-28120_FOV_ANGLE_UNITS = 'RADIANS' \begintext GALA Detector Parameters ------------------------------------------------------------------------------- GALA’s Range Finder Module (RFM) is searching for the return pulse in a range window, which is positioned approximately at the expected Time Of Flight (TOF) of the pulse. The length, or duration, of the range window is 0.04098 ms, while the sampling interval is 5 ns. \begindata INS-28100_TOF_SAMPLING_INT = 5 INS-28100_TOF_SAMPLE_INT_UNITS = 'NS' INS-28100_RANGE_WINDOW_LEN = 0.04098 INS-28100_RANGE_WINDOW_LEN_UNITS = 'MS' \begintext GALA can be configured to perform range measurements at a Pulse Repetition Frequency (PRF) varying between 1 and 50 Hz. At the nominal PRF of 30 Hz the instrument performance is best. Operation at higher and lower PRF are possible with reduced performance, e.g. pulse energy. \begindata INS-28100_NOM_PRF = 30 INS-28100_NOM_PRF_UNITS = 'HZ' INS-28100_MAX_PRF = 50 INS-28100_MAX_PRF_UNITS = 'HZ' \begintext End of IK file.