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LROC Instrument Requirements Scott Brylow, Instrument Manager Malin Space Science Systems

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The WAC monochrome mode offers 90deg FOV for full overlap poleward of 88 degrees ... Temporal movies, monochrome global morphological maps and multi-spectral images ... – PowerPoint PPT presentation

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Title: LROC Instrument Requirements Scott Brylow, Instrument Manager Malin Space Science Systems


1
LROC Instrument RequirementsScott Brylow,
Instrument ManagerMalin Space Science Systems
2
LROC Organizational Chart
3
LROC Theory of Operation
  • LROC consists of one Wide Angle Camera (WAC) and
    two Narrow Angle Cameras (NAC). All camera heads
    deliver data to the spacecraft through the
    Sequence and Compressor System (SCS).
  • The WAC subsystem consists of dual optics (UV and
    visible), providing multi-spectral images with
    100m/pixel visible resolution and 400m/pixel UV
    resolution.
  • Each NAC subsystem consists of a 2.86 FOV
    telescope, co-aligned to provide a total 5.67
    FOV, acquiring high resolution monochrome images
  • The SCS includes electronics for commanding and
    receiving data from all cameras, as well as power
    and data (SpaceWire) interfaces with the
    spacecraft.

4
LROC Solid Model
5
LROC Heritage
  • WAC heritage
  • Electronics exact copy of those used on MRO
    MARCI, other missions
  • Optics same concept, minor changes to FOV,
    filter bandpasses
  • Mechanical same mounting interface to
    spacecraft
  • NAC heritage
  • Electronics copy of those used on MRO CTX,
    single part substitution for NAC A/D, system
    clocked at higher speed.
  • Optics new design, same focal plane mounting
    interface,
  • Mechanical same concept for spacecraft mounting
    flexures
  • SCS heritage
  • New electrical design, implements MRO-heritage
    spacecraft interfaces with WAC, NAC, provides
    SpaceWire interface to LRO spacecraft.
  • New mechanical design, same concept as
    electronics boxes for NAC, WAC

6
LROC Instrument Documents
  • LRO Program Requirements Document ESMD-RLEP-0010
  • LRO Mission Requirements Document 431-RQMT-00004
  • LRO Technical Resource Allocations
    431-RQMT-000112
  • Instrument Payload Assurance Implementation Plan,
  • Instrument to Spacecraft Interface Control
    Documents
  • Mechanical 431-ICD-000090, Thermal
    431-ICD-000114, Electrical 431-ICD-000099 Data
    431-ICD-000108
  • Instrument Requirements Document MSSS-LROC-0100
  • MSSS Safety Plan MSSS-SAFE-001, April 2002
  • MSSS Quality Plan MSSS-QUAL-001, May 2004

7
LROC Mission Level RequirementsESMD-RLEP-0010
LRO Req. Level 1 Requirements Level 1 Requirements
Instr. LRO Mission Requirement Required Data Products LRO Mission Requirement Required Data Products
RLEP-LRO-M40 LROC The LRO shall obtain geodetic lunar global topography (at landing-site relevant scales - 30m down-track and 50m cross-track) with spatial resolution of 50m at the polar regions (within 5 degrees of the poles), and 1km at the equator. For limited areas of high interest (targets), provide demonstration 2m to 4m scale NAC photometric stereo Digital Elevation Models (DEM) for areas 5km x 5km.
RLEP-LRO-M40 LROC The LRO shall obtain geodetic lunar global topography (at landing-site relevant scales - 30m down-track and 50m cross-track) with spatial resolution of 50m at the polar regions (within 5 degrees of the poles), and 1km at the equator. Acquire 100m/pixel global WAC stereo imaging (in EDR format, no maps) reducible to 1km/pixel global topography. Backup for LOLA failure.
RLEP-LRO-M80 LROC The LRO shall assess meter-scale features of the lunar surface to enable safety analysis for potential lunar landing sites over targeted areas of 100km2 per the LRO Landing Site Target Specification Document. Provide up to 50 NAC Mosaics of potential landing sites with 1 m/pixel resolution.
RLEP-LRO-M80 LROC The LRO shall assess meter-scale features of the lunar surface to enable safety analysis for potential lunar landing sites over targeted areas of 100km2 per the LRO Landing Site Target Specification Document. Provide crater size density and size distribution maps of up to TBD potential landing sites.
8
LROC Mission Level RequirementsESMD-RLEP-0010
LRO Req. Level 1 Requirements Level 1 Requirements
Instr. LRO Mission Requirement Required Data Products LRO Mission Requirement Required Data Products
RLEP-LRO-M90 LROC The LRO shall characterize the Moons polar region (within 5 degrees of the poles) illumination environment at relevant temporal scales (i.e., typically that of hours) to a 100m spatial resolution and 5 hour average temporal resolution. Provide WAC uncontrolled illumination movies, 1 each of North and South Lunar Poles over the course of 1 lunar year at an average time resolution of 5 hours or better.
RLEP-LRO-M90 LROC The LRO shall characterize the Moons polar region (within 5 degrees of the poles) illumination environment at relevant temporal scales (i.e., typically that of hours) to a 100m spatial resolution and 5 hour average temporal resolution. Provide 1 m/pixel resolution NAC summer (uncontrolled) mosaics of the lunar poles (/- 4 degrees). There may be some gores in the data due to tolerance (20km) of the nominal 50km orbit altitude.
RLEP-LRO-M100 LROC The LRO shall obtain high spatial resolution global resources assessment including elemental composition, mineralogy, and regolith characteristics to a 20 accuracy and a 5km resolution. Global WAC imaging 400m/pixel in the ultraviolet (UV) bands and 100m/pixel in the visible bands, ten uncontrolled demonstration multi-spectral mosaics for high priority targets.
9
LROC Instrument System Level Requirements
Level 1 Req. Instrument Level 2 Requirements MSSS-LROC-IRD Concept/Realizability/Comment
Requirement Location LROC Instrument Measurement Requirement
M40-LROC IRD3.1.1 2m scale digital elevation models (DEM) require that NAC images be taken at varying sun angles/azimuths (at least 4 per site) Ensure repeated high-resolution images of same ground spot are acquired with NAC.
M40-LROC IRD3.1.2 100m/pixel global stereo imaging requires WAC images taken on consecutive orbits to provide overlap with similar lighting geometries WAC 90 degree FOV provides sufficient overlap to compile stereo data set, even at equator.
M80-LROC IRD3.2.1 Acquire NAC image pairs of potential landing sites with ability to identify meter-scale hazards with areal coverage of 100km2 2 NAC imagers aligned side-by-side provide 5km crosstrack, while buffer size allows 25km downtrack for 125km2 areal coverage
M90-LROC IRD3.3.1 Acquire WAC images of lunar illumination which fully overlap at latitudes gt 88 degrees and repeat frequently at latitudes gt 85 degrees so that per orbit acquisitions can be combined into a high-temporal-frequency (1 frame every 5 hours on average) movie. The WAC monochrome mode offers 90deg FOV for full overlap poleward of 88 degrees and sufficient repeat frequency poleward of 85 degrees to create movie data products
M90-LROC IRD3.3.2 Acquire NAC images for the lunar surface poleward of 86 degrees latitude during respective summers Full coverage at NAC 1 m/pixel resolution requires summing to allow downtrack of gt100 km per buffer
10
LROC Instrument System Level Requirements
Level 1 Req. Instrument Level 2 Requirements MSSS-LROC-IRD Concept/Realizability/Comment
Requirement Location LROC Instrument Measurement Requirement
M100-LROC 3.4.1 Complete global WAC maps of all visible (100m resolution) and UV (400m resolution) bands Framelet repeat rate lt0.54sec for WAC to prevent downtrack gores in the global maps. Use all filter band framelets.
M80-LROC 3.5.1 Meter-scale images of landing sites with sufficient S/N ratio so that image quality supports analysis of crater counts and sizes 50cm resolution with S/N ratio gt401 at 70deg solar incidence and albedo 0.12, 2x summing at poles to maintain adequate SNR
11
LROC Instrument Subsystem Level Requirements - I
Level 2 Req. Level 3 Requirements Concept/Realizability/ Comment
IRD Paragraph LROC Design Requirements
IRD3.1.1 4.1.1 Each NAC shall be able to acquire images at a resolution of up to 0.5 m per pixel at the nadir in the nominal LRO orbit (50 km altitude.) Requires 10 microradian IFOV and adequate spacecraft pointing accuracy
IRD3.1.1 4.3.1 The NAC images shall have a SNR of at least 401 when imaging a surface on the Moon with an albedo of 0.12 at a solar incidence angle of 70 (solar elevation angle of 20) at 50 km altitude. Large aperture (8) to get photons for high SNR
IRD3.1.1 4.4.1 Each NAC shall acquire images over a swath width of 2.5 km (5 km total for both NACs) in the cross-track direction from 50 km altitude. 2.86 degree FOV for swath width requirement
IRD3.1.2 4.1.2, 4.1.3 The WAC shall acquire images in the visible spectrum with a resolution of 100 m/ pixel (visible) and 400 m/pixel (UV) at nadir in nominal LRO orbit (50 km). Required for polar temporal illumination characterization and global morphology/color mapping
IRD3.1.2 4.4.2 From an altitude of 50 km, WAC shall have the capability to acquire contiguous images from pole to pole in each orbit. From the nominal orbit and an altitude of 50 km, WAC full-width images shall have 50 overlap with previous and subsequent orbits. 90 degree FOV provides overlap required to provide stereo data. Limited data processing planned.
IRD3.2.1 4.4.1 Down-track length of NAC images shall be limited only by the volume of the NAC-internal 256 MB buffer. Full buffer image size is 5km x 25km (no summing)
12
LROC Instrument Subsystem Level Requirements - II
Level 2 Req. Level 3 Requirements Concept/Realizability/ Comment
IRD Paragraph LROC Design Requirements
IRD3.3.1 4.4.2 From the nominal orbit and an altitude of 50 km, WAC full-width images shall have full overlap with previous and subsequent orbits poleward of 88 degrees latitude. The WAC monochrome mode provides full overlap
IRD3.3.2 4.3.1 NAC images shall have a signal to noise ratio of at least 301 when imaging a surface on the moon with an albedo of 0.12 at a solar incidence angle of 85 at 50 km altitude (with 2x summing) 8 aperture ensures enough incident energy to meet SNR
IRD3.3.2 4.4.1 Down-track length of NAC images shall be limited only by the volume of the NAC-internal 256 MB buffer. Summing to 1m/pixel allows for 100 km downtrack
IRD3.4.1 4.4.2 From the nominal orbit and an altitude of 50 km, WAC visible shall have the capability to acquire contiguous images from pole to pole in each orbit lt0.54 sec framelet timing to prevent downtrack gores
IRD3.5.1 4.1.1 The system modulation transfer function (MTF) shall be greater than 0.2 at the maximum sampling (Nyquist) frequency of the detector. Diffraction limited optics, known MTF of detector, minimal scattered light
IRD3.5.1 4.3.1 The NAC images shall have a signal to noise ratio of at least 401 when imaging a surface on the Moon with an albedo of 0.12 at a solar incidence angle of 70 (solar elevation angle of 20) at 50 km altitude. 8 aperture ensures enough incident energy to meet SNR
13
LROC Data Product Traceability
Data Description Required Inputs
Level 0 Raw unprocessed NAC and WAC Image files (EDR) from the spacecraft. Instrument data
Level 1 Calibrated Data Records (CDR) including background removal, flat fielding, absolute calibration. Calibration data, instrument and spacecraft thermal data
Level 2 Reduced Data Records (RDR) such as NAC landing site mosaics, uncontrolled best effort NAC polar summer mosaics, and WAC best effort demonstration products (small regional mosaics). Spacecraft OD and pointing data
Level 3 Temporal movies, monochrome global morphological maps and multi-spectral images created from WAC data, Photometric and radiometric adjustments performed, DEM, photogrammetric stereo analysis complete Level 1 products
14
LROC Constraints on LRO
Title Requirement Rationale Traceability
Sun Avoidance No continuous sun pointing within 30 degrees of the NACs and a minimum slew rate of 1.0 deg/sec in the instrument bore-sight. Need to keep focal plane temp below survival limits during sun-viewing. Derived by analysis
SpaceWire S/C shall be able to drain the NAC buffer in less than 160 seconds. S/C shall accept WAC packets every 0.54s. LROC NAC buffer to SCS design takes 160 seconds, S/C must keep up to prevent loss of data (no flow control in SCS implementation). LROC WAC images acquired every 0.54s with no storage mechanism except for 2 image-sized buffers in the SCS. Failure to accept WAC packets on that schedule will lead to irrevocable loss of science data. Targeting flexibility for NAC images no NAC images can be acquired while draining NAC buffer (RLEP-LRO-M40, M80)
SpaceWire Flow Control LROC shall write 8 bit data to the Transmit FIFO at a clock rate for the SpaceWire STROBE signal of 40MHz without invocation of Transmit FIFO flow control. Latency nearly zero when a packet is delivered to the SBC, we will expect a command telling us the SBC is ready for more. We can and do wait for that signal, but failure to present us with an empty buffer means well leave science data on the floor as we are acquiring as much as our downlink budget will allow. Timing diagram in Data ICD will show latency in normal use case (RLEP-LRO-M40, M80)
Pointing Accuracy /- 2.5 milli-radian 0.14, approximately 5 of a NAC FOV. Acquisition of contiguous cross-track imaging to build up areal coverage of each landing site with no gores requires pointing control to be equal to or better than planned sequence overlap to insure mosaic integrity. (RLEP-LRO-M40, M80)
Pointing Knowledge /- 0.75 milli-radian Reconstruct geometry of WAC observations to within 1 pixel. As pointing knowledge degrades geometric integrity of uncontrolled mosaics increases. Real time support of future surface operations will demand highest possible cartographic accuracy for both LROC and LOLA. (RLEP-LRO-M90, M100)
15
LROC Constraints on LRO
Title Requirement Rationale Traceability
Mount Alignment NAC1 1.42 cross-track from Nadir. NAC2 -1.42 cross-track from Nadir. Required crosstrack coverage means relative NAC alignment must be accurate to 50 NAC pixels. S/C will verify orientation of alignment cube(s). (RLEP-LRO-M40, M90)
Jitter (blur) Less than 5 micro-radian total (peak-to-peak) jitter in 0.3 milliseconds To meet resolution requirements camera/spacecraft jitter must not blur IFOV gt0.5 pixel. (RLEP-LRO-M40, M80)
Stability (geometric) Less than 10 micro-radian total (peak to peak) stability in 30 milliseconds Geometric reconstruction for landing site maps, polar maps, and stereo analysis (remove long wavelength cross-track wobble). (RLEP-LRO-M40, M80)
Timing Time of rising edge of Spacewire tickout signal to be accurately reported by corresponding time message to /- 100 milliseconds of UTC. Required to minimize overall orbital knowledge errors, which affects ability to successfully target NAC at sites of interest. Derived
Dark Signal Check Require occasional (TBD) noon-midnight nighttime images on farside for dark signal check once a month. Data can be collected in less than one minute, but all camera electronics must be at typical operating temperatures - camera remains on throughout orbit. Calibrate WAC multispectral observations to allow quantitative mineralogic interpretation for resource assessment Calibrate NAC monochrome observations to allow quantitative reflectance measurements (photometric stereo, albedo) 10 absolute, 5 relative photometric accuracy (RLEP-LRO-M40, M80, M100)
Calibration Require WAC absolute calibration with (UV and Visible) star observation for absolute calibrations. Possibly tie into same star calibration sequences for LAMP on a monthly basis. Calibration star catalog for LROC needs to be derived. Calibrate WAC multispectral observations to allow quantitative mineralogic interpretation for resource assessment 10 absolute, 5 relative photometric accuracy (RLEP-LRO-M100)
16
LROC Constraints on LRO
Title Requirement Rationale Traceability
Stereo Imaging Require 15 to 20 off-point down-track or cross-track for stereo imaging three times a day. Stereo image of same ground spot under similar lighting conditions. Issue with LOLAs coverage spec regarding time off-nadir (less than 3 of total time). Working issue. Thermally OK for 20 off-point for 20 minutes total. Stereogrammetric and photometric stereo data set generation (RLEP-LRO-M40)
Mosaicking Off-nadir pointing to get contiguous coverage over wider ground swath three times a day. Off-pointing requests would range from 2 to 20. Allow acquisition of contiguous NAC swaths to cover entire landing site error ellipses and region of surface operations. Landing Site safety (RLEP-LRO-M80)
Data Link LROC shall receive all commanding and distribute all telemetry over the SpaceWire high speed bus. Simplify spacecraft to instrument interface at GSFC request Science requirements for high resolution, high temporal resolution, etc. data require high bandwidth download (RLEP-LRO-M40, M80, M90, M100)
Data Rate LROC shall write 8 bit data to the Transmit FIFO at a clock rate for the SpaceWire STROBE signal of 40MHz without invocation of Transmit FIFO flow control. Required to deliver NAC data from SCS to use up downlink allocation, maximize science return, avoid data loss (heritage design does not use flow control). See Data ICD (RLEP-LRO-M40, M80, M90, M100)
Mass Allocation 16.5 kg with margin Includes 20 contingency over CBE. Based on proposal estimates
Science FOV NAC 2.86 per NAC, total 5.7 crosstrack. WAC 90 crosstrack. Required for swath width (RLEP-LRO-M40, M80, M90, M100)
17
LROC Block Diagram
Narrow-Angle Camera 1 (NAC1)
LVDS sync-serial
SpaceWire (to S/C CDH)
Wide-Angle Camera 2 (WAC)
Sequencing and Compression System (SCS)
RS-422
Narrow-Angle Camera 2 (NAC2)
LVDS sync-serial
18
LROC NAC Development Flow
19
LROC WAC Development Flow
20
LROC NAC Validation
  • Component / Subassembly Validation
  • Focal Length
  • Transmission
  • Bandpass filter transmission as a function of
    wavelength
  • Subsystem Validation
  • Focus and MTF -
  • Geometric - collimator w/pinhole and bar target
    sources, instrument on rotation stage
  • Radiometric - imaging a reflectance screen
    illuminated by a NIST traceable calibrated lamp
    with known geometry. Also provides flat field
    and system noise performance
  • Stray Light - imaging reflectance screen with
    fixed illumination, instrument on rotation stage
  • Orbiter Validation
  • NAC-NAC alignment locating the NAC FOVs
    accurately with respect to each other.
  • Recording and Reporting
  • Data archived locally on completion of each test
  • Data used to create instrument calibration report
    for science team and LRO mission

21
LROC WAC Validation
  • Component / Subassembly Validation
  • Geometric Distortion
  • Filter Bandpass
  • Subsystem Validation
  • Focus and MTF FPA mounted to electronics,
    system MTF measured and maximized.
  • Radiometric and Spectral - imaging a reflectance
    screen illuminated by a NIST traceable calibrated
    lamp with known geometry. Also provides flat
    field and system noise performance.
  • Stray Light - imaging reflectance screen with
    fixed illumination, instrument on rotation stage
  • Geometric Vis grid target of known geometry
    imaged. UV point source imaged on rotation
    stage
  • Environment testing as required by the GEVS
    (number?)
  • Recording and Reporting
  • Data archived locally on completion of each test
  • Data used to create instrument calibration report
    for science team and LRO mission

22
LROC Current Status
  • Trade Studies Completed
  • NAC optics aperture, bandpass, sunshade,
  • WAC filter bandpass, lens design, FOV vs.
    groundtrack
  • Pallet vs. Spacecraft Mount
  • Ongoing trade studies
  • None
  • Analysis currently being performed
  • FEM
  • Thermal
  • MTF
  • CTE
  • Current Hardware Status
  • NAC breadboard complete
  • WAC breadboard complete
  • SCS breadboard complete

23
LROC Schedule
24
LROC Summary
  • We understand the data products that must be
    produced
  • We have rigorously constructed traceability from
    the data products back to a set of design
    requirements for the instrument.
  • We understand the spacecraft environment and have
    been assured by the spacecraft that all of our
    driving requirements have been agreed to and will
    be met by the spacecraft and placed in the MRD.
  • We have a complete plan for product assurance
  • We have a complete plan for verification and
    validation of the instrument performance
    requirements
  • A breadboard exists for each individual subsystem
    (NAC, WAC, SCS)
  • High-heritage pieces of the design (NAC and WAC
    electronics) have flight hardware available
  • All spacecraft interfaces low-risk, with the data
    ICD already signed off.
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