KPL/IK BELA Instrument Kernel ============================================================================= This instrument kernel (I-kernel) contains references to mounting alignment, operating modes and timing, as well as internal geometry for the BepiColombo Laser Altimeter (BELA). Version and Date ----------------------------------------------------------------------------- Version 0.7 -- February 1, 2023 -- Ricardo Valles Blanco, ESAC/ESA Marc Costa Sitja, NAIF/JPL Fixed typos for PDS4 Bundle release version 1.0. Version 0.6 -- January 16, 2020 -- Marc Costa Sitja, ESAC/ESA Miguel Perez Ayucar, ESAC/ESA Corrected typos on FOV definitions. Version 0.5 -- August 2, 2018 -- Marc Costa Sitja, ESAC/ESA Updated boresight definitions. Version 0.4 -- December 14, 2017 -- Marc Costa Sitja, ESAC/ESA Kai Wickhusen, DLR Corrected several typos and made updates to the instrument description. Updated Receiver and Transmitter IDs. Version 0.3 -- February 15, 2017 -- Marc Costa Sitja, ESAC/ESA Added instrument description and corrected FOV definitions. Preliminary version to be checked by the BELA team. Version 0.2 -- September 23, 2016 -- Marc Costa Sitja, ESAC/ESA Updated BEPICOLOMBO MPO IDs from -69 to -121. Removed kernel name and version assignment. Version 0.1 -- February 08, 2016 -- Jonathan McAuliffe, ESAC/ESA Channel ID-mixup corrected. Version 0.0 -- February 11, 2013 -- Jonathan McAuliffe, ESAC/ESA Initial prototype. References ----------------------------------------------------------------------------- 1. ``Kernel Pool Required Reading'', NAIF. 2. BepiColombo MPO Spacecraft Frames Definition Kernel 3. ``Frames Required Reading'', NAIF. 4. ``C-Kernel Required Reading'', NAIF. 5. ``BELA Instrument User Manual'', H. Hussmann, R. Schrodter, DLR, Issue 3, Revision 0, 23th August 2017 6. ``BELA Experiment Interface Document B (EID-B)'', Issue 1, 20th July 2012 7. ``BELA Pointing and Alignment Document'', Issue 1, Revision 2, 24th November 2008 8. ``BC-ASD-DW-00074_B_MPO_OPTB_RELEASED'', Technical Drawing, Astrium, 3rd July 2007. Contact Information ----------------------------------------------------------------------------- If you have any questions regarding this file contact the ESA SPICE Service at ESAC: Alfredo Escalante Lopez (+34) 91-8131-429 spice@sciops.esa.int or NAIF at JPL: Boris Semenov +1 (818) 354-8136 Boris.Semenov@jpl.nasa.gov Implementation Notes ----------------------------------------------------------------------------- This file is used by the SPICE system as follows: programs that make use of this frame kernel must "load" the kernel normally during program initialization. Loading the kernel associates the data items with their names in a data structure called the "kernel pool". The SPICELIB routine FURNSH loads a kernel into the pool as shown below: FORTRAN: (SPICELIB) CALL FURNSH ( frame_kernel_name ) C: (CSPICE) furnsh_c ( frame_kernel_name ); IDL: (ICY) cspice_furnsh, frame_kernel_name MATLAB: (MICE) cspice_furnsh ( 'frame_kernel_name' ) PYTHON: (SPICEYPY)* furnsh( frame_kernel_name ) In order for a program or routine to extract data from the pool, the SPICELIB routines GDPOOL, GIPOOL, and GCPOOL are used. See [1] for more details. This file was created and may be updated with a text editor or word processor. * SPICEYPY is a non-official, community developed Python wrapper for the NAIF SPICE toolkit. Its development is managed on Github. It is available at: https://github.com/AndrewAnnex/SpiceyPy Naming Conventions ----------------------------------------------------------------------------- All names referencing values in this I-kernel start with the characters 'INS' followed by the NAIF BepiColombo spacecraft ID number (MPO: -121; MM0: -68) and then followed by a NAIF three digit codes for the BELA instrument: BELA BASE (100), BELA RECEIVER (101), BELA TRANSMITTER (102). The remainder of the name is an underscore character followed by the unique name of the data item. For example, the BELA RECEIVER boresight direction in the MPO_SPACECRAFT frame (see [3]) is specified by: INS-121101_BORESIGHT The upper bound on the length of the name of any data item identifier 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. Description ----------------------------------------------------------------------------- From [5]: BELA for the first time will return a digitized laser reflection signal (only in a dedicated instrument mode in order to keep the overall data volume moderate). This will allow characterizing the surface roughness with unprecedented detail and accuracy. BELA's albedo measurement capability will be particularly important for permanently shaded craters where ice is suspected to be found. Here, BELA can observe with its laser where most other remote sensing instruments will fail to obtain a signal. In its normal operational mode, BELA employs a modified digital filter matching algorithms for return pulse detection, while other similar instruments (MOLA, MLA) use analog filter matching. The digital filters can be exchanged at any time by telecommand and/or parameter upload. BELA uses the 'direct-detection' (classical) approach to laser altimetry. High power pulses (50 mJ) at 1064 nm are emitted from active Q-switched Nd:YAG laser at nominally 10 Hz. The emission time of each pulse is measured by the receiver though its APD, analog front-end electronics and the digital rangefinder board. This ensures that aging effects of the electronics are self-compensated. The beam is reflected from the surface (surface spot size ~20-50 m) and received around 5 ms later at a 20 cm diameter telescope. The image is refocused onto a silicon avalanche photodiode through a narrow band pass interference filter. The signal is then sampled and fed to a digital ragefinder electronics. This system determines the time of flight (and therefore range), the integrated pulse intensity, and its width. The data are passed to a digital processing unit which controls the operation and services the spacecraft interface. The experiment requires significant baffling and thermal control but can operate over the dayside hemisphere (with only slightly reduced signal to noise) allowing optimum data acquisition over a minimum duration. BELA will provide < 1 m range resolution which is commensurate with the expected knowledge of the spacecraft position. Optimum data return is expected at altitudes up to at least 1100 km above the surface. Samples will be acquired about every 250 m on ground- tracks separated by 25 km at the equator (crossing at the poles). Over the lifetime of the mission, data points will be 6 km apart (decreasing with latitude). The experiment will provide return pulse intensity and width information allowing an assessment of surface albedo and roughness at ~20 - 50 m scales including in un-illuminated polar craters. BELA is a laser altimeter following the classical approach of direct detection: a relatively strong laser pulse (50 mJ @ 2 to 8 ns) is fired towards the surface, and a telescope of ~200mm diameter receives the returned signal, transfers it to an avalanche photo diode (APD) and finally into a rangefinder electronics. With BELA four principally different physical quantities will be determined by sending laser shots to Mercury's surface and measuring the delay, intensity and the curve characteristics of the returned signal. - height of surface with respect to the Mercury reference radius, - surface slope, - surface roughness, - albedo. BELA instrument consists of the following units (a 'unit' is a box or other hardware element that has a direct mounting interface to the S/C): - BPU (Baseplate Unit; consists of a mechanical structure - the baseplate - which carries the telescope (RTL), the laser head box (LHB) and the focal plane assembly (FPA) where the detector (DET) and the back-end optics (BEO) are located. - TBU (Transmitter Baffle Unit) - SPU (Straylight Protection Unit) - RBU (Receiver Baffle Unit) - AEU (Analogue Electronics Unit) - LEU (Laser Electronics Unit; a common electronics box) ELU (Electronics Unit; a common electronics box) The following table summarizes the instrument optics, performances and resolution: Parameter | Units | Value/Description Remarks -------------------------+---------------+---------------------------- Laser Source | | | | Material | | Nd:YAG Q-Switch | | Active Laser pump | | Side Pumped Wavelenght | nm | 1064 Pulse energy BOL | mJ | >= 50 Pulse energy EOL | mJ | >= 40 Pulse frequency | Hz | 10 (nominal value; can be | | changed via telecommand) Pulse duration | ns | 3-8 Beam divergence | micro rad | 50 +/- 10 (full cone) Beam diameter | mm | >= 74 mm (1/e^2) at of BEX. | | BEX aperture is 85 mm in | | diameter Transmitter optics | | BK7-G18, F2-G12, LF5-G15, materials | | fused silica Lenses coating | | Nd:YAG AR-coating | | Receiver Optics | | | | Telescope Aperture | mm | 204 Focal Length | mm | 1250 Field of View | micro rad | 530 (full cone) Design | | Ritchey-Chretien type Material | | Optical Grade pure Beryllium Surface Coating | | Gold Optics transmission | % | > 70 Notch filter | nm | +/- 0.37 nm around the bandwidth | | central wavelength (or .74 | | nm in short) Notch filter | % | > 70 transmission | | | | Receiver Detector | | | | Detector type | | Silicon Avalanche Photodiode Digital resolution | bit | 8 Time resolution | bit | 2 | ns | 2 Active Area | um | 800 Physical Size | inch | 1 Responsivity | A/W | > 50 Response Uniformity | % | +/- 10 (Over active area) Cooling | | Peltier TEC Cooling Power Req. | W | <= 0.9 Mounting Alignment ----------------------------------------------------------------------------- Refer to the latest version of the BepiColombo Frames Definition Kernel (FK) [4] for the BELA reference frame definitions and mounting alignment information. FOV Definitions ----------------------------------------------------------------------------- This section contains assignments defining the BELA transmitter and receiver FOVs. These definitions are based on the parameters provided in the previous sections and are provided in a format consistent with/required by the SPICE TOOLKIT function GETFOV. Those two fields of view shall be defined as half angle of a cone centred on the boresight direction. BELA Receiver (MPO_BELA_RECEIVER) FOV: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Please note that the FOV reference and cross angles are defined with half angle values (half cone). The following FOV definition corresponds to the NAIF Body Names: MPO_BELA_RECEIVER. \begindata INS-121101_NAME = 'MPO_BELA_RECEIVER' INS-121101_BORESIGHT = ( 0.0, 0.0, -1.0 ) INS-121101_FOV_FRAME = 'MPO_BELA_RECEIVER' INS-121101_FOV_SHAPE = 'CIRCLE' INS-121101_FOV_CLASS_SPEC = 'ANGLES' INS-121101_FOV_REF_VECTOR = ( 0.0, 1.0, 0.0 ) INS-121101_FOV_REF_ANGLE = ( 0.000265 ) INS-121101_FOV_ANGLE_UNITS = 'RADIANS' \begintext BELA Transmitter (MPO_BELA_TRANSMITTER) FOV: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Please note that the FOV reference and cross angles are defined with half angle values. The following FOV definition corresponds to the NAIF Body Names: MPO_BELA_TRANSMITTER. \begindata INS-121102_NAME = 'MPO_BELA_TRANSMITTER' INS-121102_BORESIGHT = ( 1.0, 0.0, 0.0 ) INS-121102_FOV_FRAME = 'MPO_BELA_TRANSMITTER' INS-121102_FOV_SHAPE = 'CIRCLE' INS-121102_FOV_CLASS_SPEC = 'ANGLES' INS-121102_FOV_REF_VECTOR = ( 0.0, 1.0, 0.0 ) INS-121102_FOV_REF_ANGLE = ( 0.000025 ) INS-121102_FOV_ANGLE_UNITS = 'RADIANS' \begintext End of IK file.