KPL/IK ORX REXIS Instrument Kernel =============================================================================== This Instrument Kernel (IK) file contains Field-Of-View (FOV) and other geometric parameters definitions for the Regolith X-ray Imaging Spectrometer (REXIS) instrument. Version and Date ------------------------------------------------------------------------------- Version 0.1 -- Oct 9, 2018 -- Daniel Hoak, CfA Descriptions, diagrams, and updated FoV definitions for ORX_REXIS and ORX_REXIS_SXM detectors. Version 0.0 -- August 24, 2015 -- Boris Semenov, NAIF Placeholder version. References ------------------------------------------------------------------------------- 1. Kernel Pool Required Reading 2. GETFOV, getfoc_c, cspice_getfov headers 3. OSIRIS-REX Spacecraft Frames Definition Kernel 4. Masterson, R.A., Chodas, M., Bayley, L. et al. Space Sci Rev (2018) 214: 48. https://doi.org/10.1007/s11214-018-0483-8 Contact Information ------------------------------------------------------------------------------- Daniel Hoak, Harvard CfA, (617)-496-1821, daniel.hoak@cfa.harvard.edu Boris V. Semenov, NAIF/JPL, (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 kernel must ``load'' the kernel, 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 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. This file was created and may be updated with a text editor or word processor. Naming Conventions ------------------------------------------------------------------------------- All names referencing values in this IK file start with the characters `INS' followed by the NAIF ORX ID number (-64) followed by a NAIF three digit ID code for one of REXIS detectors: ORX_REXIS -64330 ORX_REXIS_SXM -64340 The remainder of the keyword name is an underscore character followed by the unique name of the data item. For example, the boresight direction of ORX_REXIS_SXM is specified by: INS-64340_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 ------------------------------------------------------------------------------- The REXIS instrument has two components: a coded-mask x-ray spectrometer composed of four CCDs with 1024x1024 pixels each, and a Solar X-ray Monitor (SXM) x-ray spectrometer composed of a single detecting element. The CCD detector is mounted at the base of a 20cm tower. At the top of the tower is a coded aperture mask of stainless steel. REXIS uses a coded aperture mask to provide high throughput and high angular resolution over a wide field of view. The REXIS CCDs are MIT Lincoln Labs CCID-41s in a 2x2 array. The quantum efficiency is >0.3 for 0.3keV to 10keV energy band. REXIS has a 320nm aluminum optical blocking filter (OBF) applied directly to the top surface of the CCDS to block optical photons. The OBF reduces the detectable x-ray flux at low energies. The SXM is an Amptek SDD (the same detector technology used on the NICER mission), with an effective area of about 17mm^2. The SXM SDD is packaged within a Ni housing that holds a 5x5mm, 12.7um thick beryllium window. A collimator restricts the full-width maximum intensity (FWMI) FoV to 42deg through a 1mm pinhole aperture. The SXM useful energy range is 1.0keV to 23keV in 512 bin histogram, spanning (mathematically) -5.9keV to 23.6keV, in 58eV/bin. Mounting Alignment ------------------------------------------------------------------------------- Refer to the latest version of the ORX Frames Definition Kernel (FK) [3] for the instrument reference frame definitions and mounting alignment information. Briefly, the REXIS SXM is mounted near the ORX HGA, and the SXM boresight is aligned with the ORX +X axis. The REXIS x-ray imaging spectrometer is mounted on the ORX instrument deck. The REXIS boresight is aligned with the ORX +Z axis, and the REXIS X-Y plane is rotated ten degrees counterclockwise with respect to the ORX X-Y plane. Instrument Detector/Sensor Layout (if applicable) ------------------------------------------------------------------------------- The REXIS coded-aperture mask is 9.84cm in diameter, with 50% open fraction. Mask pixels are 1.536mm squares, and the mask is 64 pixels across. The coded region (with open pixels) is a circular area, 64 pixels in diameter. 50% of the pixels in this region are "open". The mask is located at the top of the REXIS instrument tower, 20cm above the REXIS CCD detector plane. The REXIS detector is composed of 4 CCD detectors, 1024x1024 pixels each, arranged in a 2x2 grid. Detector pixels are 0.024mm, and each CCD detector is a 2.4576cm square. The CCDs are subdivided into "nodes". There are four nodes per CCD, and each node is 256x1024 pixels. The nodes are read-out along the REXIS x-direction. Of the 16 REXIS nodes, ten are capable of returning valid science data. The other six nodes are typically disabled in software and do not record x-ray events. The field of view (FoV) for a given CCD pixel is defined by the circle of the coded aperture mask. Each pixel has a circular FoV with a half-extent of approximately 13.5deg. There is a slight variation in the size of the FoV for each pixel, depending on its location relative to the mask (pixels directly under the center of the mask have a slightly larger FoV than pixels at the edge of the detector). Here is a diagram of the REXIS instrument tower from the view of the REXIS x-z plane: Coded mask --------|-|-|-||--||-|-||--------- | | | | | | | | | | | | | | | | | | | | 20 cm from detector plane | | to mask (not to scale) | | | | | | | +Zrexis | | ^ | | | | | | | | =========--> +Xrexis | +Yrexis is into the page. ---------------------------------- CCD Array Here is a diagram of the REXIS CCD detector in the REXIS x-y plane, looking down from the mask: CCD2 CCD3 ---------------- --------------- | | | | | | | | | | | | | | | | Each CCD is 2.4576cm on a side | | | | | |y| | | |^| | ----------------|--------------- o-->+Xrexis +Zrexis is out of the page. ---------------- --------------- | | | | | | | | | | | | | | | | | | | | | | | | | | | | ---------------- --------------- CCD1 CCD0 Here is the same diagram of the REXIS detector plane, with the CCD sub-nodes labeled. Each node has different noise and energy resolution characteristics. The non-functioning nodes are marked with 'XXXXX' (e.g., all of CCD3 is non-functioning). CCD2 CCD3 ---------------- --------------- |node3 XXXXXXXX| |node0 XXXXXXX| |..............| |.............| |node2 | |node1 XXXXXXX| |..............| |.............| |node1 | |node2 XXXXXXX| |..............|y|.............| |node0 |^|node3 XXXXXXX| ----------------|--------------- o-->+Xrexis ---------------- --------------- |node3 | |node0 XXXXXXX| |..............| |.............| |node2 | |node1 | |..............| |.............| |node1 | |node2 | |..............| |.............| |node0 | |node3 | ---------------- --------------- CCD1 CCD0 Instrument CCD and Mask Parameters ------------------------------------------------------------------------------- TBD. Instrument Pixel-to-3D Coordinate Mapping ------------------------------------------------------------------------------- TBD. Instrument Node Parameters ------------------------------------------------------------------------------- TBD. Instrument FOV Definition(s) ------------------------------------------------------------------------------- This section defines the REXIS FOVs. The REXIS field of view (FoV) defined here is the full width half intensity (FWHI). Objects within this region of the sky will illuminate a minimum of half of the REXIS detector plane. Here the FWHI is defined under the assumption that all REXIS CCDs are enabled. The FWHI FoV can be approximated by a circle with a diameter of 27.6deg, centered on the REXIS boresight. The definition below uses the half-extent (13.8deg), extending from the REXIS +z axis. The SXM field of view is defined as the full width maximum intensity (FWMI). Objects inside this field of view will fully illuminate the SXM detector. Objects outside this field of view will only partially illuminate the SXM, if at all. The SXM FWMI FoV is a circle 42deg in diameter, centered on the SXM boresight. Note the SXM boresight is the +z SXM axis, defined in the SXM coordinate frame (which is different than the REXIS coordinate frame). The definition below uses the half-extent angle (21deg), extending from the SXM +z axis. ID SHAPE FRAME SIZE BSIGHT SOURCE ------- -------- ------------- -------- ------ ------------- -64330 CIRCLE ORX_REXIS 13.8 +Z REXIS SSR paper -64340 CIRCLE ORX_REXIS_SXM 21.0 +Z REXIS SSR paper where the source means: REXIS SSR paper -- REXIS publication in Space Science Reviews [4] All sizes are half-extents given in degrees. The FOVs are defined in this data block. \begindata INS-64330_FOV_CLASS_SPEC = 'ANGLES' INS-64330_FOV_SHAPE = 'CIRCLE' INS-64330_FOV_FRAME = 'ORX_REXIS' INS-64330_BORESIGHT = ( 0.0, 0.0, 1.0 ) INS-64330_FOV_REF_VECTOR = ( 1.0, 0.0, 0.0 ) INS-64330_FOV_REF_ANGLE = ( 13.8 ) INS-64330_FOV_ANGLE_UNITS = ( 'DEGREES' ) INS-64340_FOV_CLASS_SPEC = 'ANGLES' INS-64340_FOV_SHAPE = 'CIRCLE' INS-64340_FOV_FRAME = 'ORX_REXIS_SXM' INS-64340_BORESIGHT = ( 0.0, 0.0, 1.0 ) INS-64340_FOV_REF_VECTOR = ( 1.0, 0.0, 0.0 ) INS-64340_FOV_REF_ANGLE = ( 21.0 ) INS-64340_FOV_ANGLE_UNITS = ( 'DEGREES' ) \begintext End of the IK file.