Transcript Instrument Requirements - The (New) People's Liberation

LRO System Requirements Review
Lunar Orbiter Laser Altimeter (LOLA)
Investigation Requirements & Implementation
John Cavanaugh
LOLA Instrument Systems Engineer
NASA GSFC
NASA’s Goddard Space Flight Center
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LOLA Organization Chart
NASA’s Goddard Space Flight Center
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LOLA Overview
Functional Description
LOLA Instrument
Using a single pulsed laser split into five beams
LOLA will measure :
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Range to the Lunar Surface
– Pulse time of flight method
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Single threshold crossing
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Beam Expander
Each measurement referenced to S/C MET
Surface Direct Reflectance
– Transmitted laser energy before splitter
– Received signal energy from each of five detectors
Receiver
Telescope
Laser Bench
Detectors &
Aft Optics
Main Optical
Bench
(2 more on far side)
Lunar Digital Elevation Model
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Radiator
leading edge & trailing edge timing
From these measurements and LRO S/C data
products the LOLA Science team will produce :
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DOE Beam Splitter
Localized surface roughness and slope data for landing site
characterization
Surface reflectance data
Imaging of permanently shadowed regions
S/C Deck
Main Electronics Box
Lunar geodetic coordinate system
LRO precision orbit and trajectory
Lunar gravity model
NASA’s Goddard Space Flight Center
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LOLA Heritage
Heritage Design Elements
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Laser : MLA, GLAS, SLA, MOLA
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Receiver Telescope : MLA
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Low-speed coarse counter
High resolution ASIC
Power Converters : MLA, GLAS, MOLA
Signal Processing Algorithm : MLA, MOLA
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SiAPD hybrid with programmable gain (MLA, GLAS)
Range Measurement Unit : MLA
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Refractor design
Beryllium tube
Fiber coupling to aft optics
Detector : MLA, GLAS, SLA, MOLA
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DPSSL Nd:YAG slab oscillator
Crossed-porro resonator configuration
Passive Q-switch ( MLA, GLAS )
Laser diodes from Coherent ( MLA )
Beryllium beam expander telescope ( MLA )
Range gate tracking
Active gain & threshold control with signal & noise feedback
Implemented in 80C196 (MLA), 8086 (MOLA),
80K85 (LOLA)
Beryllium structure : MLA, GLAS, MOLA
NASA’s Goddard Space Flight Center
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LRO-LOLA Instrument Document Tree
LRO Project Requirements
ESMD-RLEP-0010
LOLA Science and Functional
Requirements
LOLA System
Implementation Plan
LOLA-RQMT-0002
LOLA-PLAN-000N
LRO Pointing and Alignment
Requirements
LRO E ICD
LRO M ICD
LRO Gnd Sys ICD
431-ICD-00008
431-ICD-000NN
431-ICD-00049
LOLA Configuration Management
Plan
LOLA Performance Assurance
Implementation Plan
LOLA-PLAN-0001
LOLA-PLAN-0003
LOLA Integration and Test Plan
LOLA System Engineering
Management Plan
LOLA EICD
LOLA TICD
LOLA MICD
LOLA DICD
431-ICD-00098
431-ICD-000117
431-ICD-000089
431-ICD-00108
LOLA Interface Drawings
LOLA Assembly Drawings
LOLA Sub-Assembly Drawings
LOLA-PLAN-00NN
LOLA-PLAN-0010
LOLA Safety Plan
LOLA-PLAN-00NN
LOLA Risk Management Plan
LRO CM DOC’S
LRO Technical Resource Allocations
431-RQMT-00112
LOLA
Component
Drawings
LOLA
Schematics
LOLA CM DOC’S
LRO Mission Requirements Document
431-RQMT-00004
LOLA-PLAN-00NN
LOLA Contamination Control Plan
LOLA-PLAN-0004
NASA’s Goddard Space Flight Center
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LRO Document Flowdown
(Lamp’s version)
Level
1
2
2
2
2
2
2
2
2
3
3
3
3
Document Number
ESMD-RLEP-0010
431-RQMT-000004
11239-IRD-01
431-SPEC-000112
431-OPS-000042
431-SPEC-000016
431-SPEC-000012
431-RQMT-000113
430-RQMT-000006
431-ICD-000087
431-ICD-000115
431-ICD-000096
431-ICD-000106
NASA’s Goddard Space Flight Center
Title
LRO Program Requirements Document
LRO Mission Requirements Document
LAMP Instrument Requirements Document
LRO Technical Resource Allocation Specification
LRO Mission Concept of Operations
LRO Electrical Power Subsystem Spec
LRO Mechanical Systems Specification
LRO Pointing and Alignment Specification
RLEP Mission Assurance Requirements Document
LAMP Mechanical Interface Control Document
LAMP Thermal Interface Control Document
LAMP Electrical Interface Control Document
LAMP Data Interface Control Document
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Mission Level Requirements
ESMD-RLEP-0010
LRO
Req.
Level 1: Requirements
Instr.
LRO Mission Requirement
Data Products
RLEPLRO-M30
LOLA
The LRO shall collect global geodetic data
using spatially resolved topography with a 10m
vertical accuracy with a 2km cross-track and
30m along track sampling at the equator.
Global digital elevation model of the moon with 1
m vertical resolution and 100 m horizontal
resolution with 1 km average cross track
sampling at the equator.
RLEPLRO-M40
LOLA
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.
Global topography with 1 m vertical resolution
and 100 m horizontal resolution with 1 km
average cross track sampling at the equator.
RLEPLRO-M60
LOLA
The LRO shall obtain landform-scale imaging of
lunar surfaces in permanently shadowed
regions at 50m spatial resolution.
Digital elevation model of topography in
permanently shadowed polar regions with 50m
horizontal resolution, 1m vertical resolution
RLEPLRO-M70
LOLA
The LRO shall identify putative deposits of
appreciable near-surface water ice in the
Moon’s polar cold traps at a 100m spatial
resolution.
Reflectance data from the permanently
shadowed regions (PSRs) to identify surface ice
signatures at a limit of 4% ice surface coverage
by area
NASA’s Goddard Space Flight Center
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Mission Level Requirements
ESMD-RLEP-0010
LRO
Req.
Level 1: Requirements
Instr.
LRO Mission Requirement
Data Products
RLEPLRO-M80
LOLA
The LRO shall assess meter-scale features
of the lunar surface to enable safety analysis
for potential lunar landing sites over targeted
areas of 100km^2 per the LRO Landing Site
Target Specification Document.
Topography, surface slopes, and surface
roughness at 25-m spacing over a 70-m wide field
of view (FOV) swath at up to 50 selected potential
landing sites.
RLEPLRO-M90
LOLA
The LRO shall characterize the Moon’s 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.
Map of the polar regions poleward of latitudes 86°
with a vertical resolution of 10 centimeters (cm) and
a spatial resolution of 25 to 35m after one year,
which will identify potential sites of optimal solar
power generation.
NASA’s Goddard Space Flight Center
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LOLA System Level Requirements
Level 1
Req.
Instrument Level 2: Requirements
Requirement
no. or para.
LOLA Instrument Measurement Requirement
IMR1a: Provide range measurement from the LRO orbit to
the lunar surface with better than 1 m vertical accuracy.
Laser pulse time-of-flight
measurement, each pulse
time referenced to S/C MET
IMR1b : Provide range measurements with an along track
posting of ≤30 m from the 50 km nominal LRO altitude.
28 Hz pulse repetition rate,
beam pattern
IMR2
Provide range measurements at the above (IMR1) ranging
accuracy and sampling rate continuously with ≥95% single
sample spot detection probability for one year to achieve an
average ground track spacing of ~1 km at the equator and
<100 meter spacing within 5 degrees to the poles
Design such that SNR > 3dB
and Pd > 95%. Drives laser
energy and receiver aperture
IMR3
Provide the geodetic location of each laser footprint on the
lunar surface to within the laser footprint size.
Time stamp each pulse wrt
S/C MET
IMR5
Provide a global digital elevation model (DEM) with 1 m
vertical resolution and <1/25°x1/25° grid spatial resolution.
Product of range
measurement with orbit &
pointing knowledge
IMR1
M30-LOLA
M40-LOLA
M90-LOLA
Concept/Realizability/Comment
LOLA-RQMT-0002
NASA’s Goddard Space Flight Center
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LOLA System Level Requirements
Level 1
Req.
Instrument Level 2: Requirements
Requirement
no. or para.
LOLA Instrument Measurement Requirement
IMR6
Provide lunar surface reflectance measurements of the laser
pulses at better than 10% relative accuracy (shot to shot and
spot to spot) for received energy greater than 0.1 fJ in
permanently shadowed regions of the lunar surface.
Pulse integrator circuit on
transmit & receive channel.
IMR4
Provide five separate laser spots on the lunar surface from
each laser pulse and measure the time of flight from each
spot. The size of each laser spot is 5 meters (±1m) in
diameter and separated by 25 meters center to center at 50
km nominal spacecraft altitude
Beam splitter after laser
provides far field pattern.
IMR7
Provide better than 10 cm resolution range and return pulse
width measurement on single shot and each spot to assess
slope and surface roughness characteristics.
Measure leading & trailing
edge pulse timing on each
received pulse
IMR8
Provide means to verify optical alignment between LOLA &
LROC
Alignment cube
M70-LOLA
M60-LOLA
M80-LOLA
M90-LOLA
Concept/Realizability/Comment
LOLA-RQMT-0002
NASA’s Goddard Space Flight Center
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LOLA System Level Requirements
Level 2a: Requirements LOLA-RQMT-0002
Level 2
Req.
Reqt.
no.
IMR1
IMR2
IMR4
IMR8
IMR3
IMR5
MRD-040
Concept/Realizability/Comment
LOLA Instrument Functional Requirement
F3
Measure laser pulse time of flight (TOF) with better than 500 ps
resolution from 0 to 5 milliseconds wrt laser trigger pulse.
Coarse ctr. @ 20 MHz with
TDC fine counter
F6
Laser pulse repetition rate = 28 Hz ±0.1 Hz
By design
F8
Pd>95% from 20 to 80 km altitude
Laser energy & Rx aperture
F7
Produce five laser footprints each with 5m diameter +/- 0.5m nadir
pointing with 25m +/-1m spacing between adjacent spots at 50km
altitude.
Beam splitter w/ pattern
aligned to LRO velocity
F2
Determine laser pointing wrt LRO spacecraft reference to within 100
µrad
Alignment cubes, on-orbit
cal.
F12
Crosstalk between any two channels < 1%
Beam spacing, Rx FOV
F1
Time stamp laser pulses to better than ±100 microseconds with
respect to the LRO S/C 1 second timing reference.
Synchronize LOLA counters
to MET pulse
F5
Total ranging error < 1 m w/ nadir pointing and post processing of
S/C orbit and attitude.
Synch. Measurements w/
LRO pointing & orbit data
F9
Maintain long term ranging bias error to ≤ 1 m over the mission
lifetime.
LRO USO stability
NASA’s Goddard Space Flight Center
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LOLA System Level Requirements
Level 2a: Requirements LOLA-RQMT-0002
Level 2
Req.
Reqt.
no.
IMR6
IMR7
Concept/Realizability/Comment
LOLA Instrument Functional Requirement
F10
Measure the transmitted laser energy with better than 5% (1 sigma)
relative accuracy (shot to shot).
F11
Measure the received energy in each return signal with 5% (1 sigma)
relative accuracy for received energies Er Such that 0.1fJ < Er < 10 fJ
F4
Measure receive pulse widths from 6 to 100 ns with better than 0.5 ns
resolution
NASA’s Goddard Space Flight Center
Pulse integrator
TDC
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LOLA Subsystem Level Requirements
Transmitter
Level 3: Requirements LOLA-RQMT-0002
Level 2
Req.
Reqt
no.
F3, F4, F6,
F7, F8
Concept/Realizability/Comment
Laser Design Requirements
L1
Wavelength 1064.3 nm ±0.1nm
Nd:YAG fundamental
L2
Configuration : Diode Pumped Solid State Cr:Nd:YAG
Efficiency
F7, F8
L3
Pulse energy before beam expander : 2.7 mJ ±0.3 mJ
Signal link
F6
L4
Pulse rate : 28.0 Hz ±0.1 Hz
For coverage
F3, F4
L5
Pulse width : 6 ns ±2 ns
Timing resolution
F7, F12
L6
Output beam divergence : 1.8 mrad ±0.2 mrad
Sample size on moon
F7, F12
L7
Spatial mode : TEM00
Radially symmetric sample
F7
L8
Beam diameter : 1 mm ±0.2 mm
Beam expander input
F8
B1
Transmission efficiency > 13% per spot
Req’d to meet signal link
L3, L9
B2
Input energy density NTE 0.6 J/cm2
Below damage threshold
F7
B3
Output beam divergence : 100 rad ±10 rad
5 m spots at 50 km
F7, F12
B4
Beam separation wrt center beam : 500 rad ±20 rad
Coverage
F7
B5
Pattern clocking wrt instrument coordinates : 26° ±2°
Sample pattern
NASA’s Goddard Space Flight Center
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LOLA Subsystem Level Requirements
Receiver
Level 3: Requirements LOLA-RQMT-0002
Level 2
Req.
Concept/Realizability/Comment
Laser Design Requirements
Reqt no.
F3, F7,
F8
RE01
Receiver aperture > 0.015 m2
14 cm diameter refractive
telescope similar to MLA
F7
RE02
Receiver PFOV : 1.4 mrad
Defines telescope size
F7, F8,
F12
RE02a
Receiver IFOV (each detector) : 400 rad ±20 rad
To match transmitter pattern
F8
RE03
Detector quantum efficiency ≥ 40%
Signal link (photon detection)
F8
RE04
Optics transmission ≥ 70%
Signal link (throughput)
F8
RE06
Filter bandwidth ≤ 0.8 nm FWHM
Signal link (minimizes
background)
F8
RE07
Transmission loss due to contamination ≤0.5 dB up to launch
Signal link (throughput)
F8
RE08
Transmission loss due to misalignment ≤0.5 dB up to launch
Signal link (misalignment)
F12
RE09
Receiver crosstalk < 1%
NASA’s Goddard Space Flight Center
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LOLA Subsystem Level Requirements
Signal Processing
Level 3: Requirements LOLA-RQMT-0002
Level 2
Req.
Concept/Realizability/Comment
Laser Design Requirements
Reqt no.
F1
RSP1
Time stamp laser pulses to within ±100s of LRO 1 PPS
For post-processing location
F3, F4
RSP2
Time of flight resolution better than 500 ps
Aperture uncertainty portion of
10 cm error, defines TDC
F3, F4
RSP3
Receiver impulse response 6 ns FWHM
Required for resolution,
amplifier detector bandwidth
140 MHz
F5, F9
RSP4
OCXO frequency drift ≤10-7 over single shot measurement
And ≤10-7 over 3 hours
Short and midterm OCXO
stability
F3, F7,
F8
RSP5
Capture and characterize one return per shot per detector
Link margin high, processing
like MOLA
F3, F4
RSP6
Measure signal pulse widths from 6 to 100 ns
Minimum to 3X expected max
F10
RSP7
Measure laser output energy with better than 5% relative accuracy
F11
RSP8
Measure return pulse energy with better than 5% relative accuracy
Shot to shot relative accuracy
required for expected ice
reflectivity measurement
F3
RSP9
Measure pulse time of flight from 0 to 5 ms full range
Encompasses checkout &
extended mission orbits X 4
F8
RSP10
Programmable detector voltage gain from 0.1 to 10 with linear
response from 0.3 to 10
VGA implementation same as
MLA, GLAS
NASA’s Goddard Space Flight Center
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LOLA Data Product Traceability
Data
Level 0
Level 1
Level 2
Level 3
Level 4
Description
Each shot :
-Leading & trailing edge signal event counts
-Transmitted pulse energy ADC counts
-Received pulse energyADC counts
Each second :
- Background noise counts, threshold ADC readbacks, event counts
- Housekeeping counts of T, I, V, laser pump
Housekeeping values converted to engineering units
Event counts converted to delay times in seconds
Energy counts converted to Joules
Background counts converted to Watts
Range measurements converted to altitude
Range measurements converted to pulse spread values
Energy measurements converted to reflectance
1st iteration of surface location
Initial DEM products:
- Topography
- Slope
- Surface roughness
- Reflectance
- LRO precision orbits and trajectory files
Parameter set defining lunar geodetic coordinate system
Global topography model & spherical harmonic coefficients
Global gravity model & spherical harmonic coefficients
NASA’s Goddard Space Flight Center
Required Inputs
LRO LOLA telemetry
LOLA calibration data
LRO: Time, orbit and attitude products
LOLA crossover analysis
LRO: POD products
LOLA DEM products
LRO precision orbits and trajectory files
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LOLA Constraints on LRO
• Provide stable timebase frequency for LOLA range measurement
• Operate LOLA continuously throughout the measurement phase.
• Maintain S/C pointing within ±1° of nadir for >97% of the measurement phase.
• Provide post-processed pointing knowledge to within 150 µrad each axis (3-sigma) at 1 second
intervals.
• Angular Exclusion : 1.5 millirads around boresight.
• Align LOLA beam pattern to within ±1° of S/C velocity vector.
• Provide precision positioning knowledge data of LRO spacecraft for post-processing of LOLA data.
• Provide a 1 PPS time signal and associated MET message on orbit.
• Provide post-processed time with 3 ms accuracy relative to UTC.
• Provide means to reference LOLA optical axis to S/C coordinates during I&T
NASA’s Goddard Space Flight Center
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LOLA Block Diagram
NASA’s Goddard Space Flight Center
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LOLA Development Flow
NASA’s Goddard Space Flight Center
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LOLA Verification
TESTING (Levels):
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Ranging Performance (Instr. & S/C):
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Signal Processing (Instr. & S/C):
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Monitor laser output energy with calibrated GSE meter.
Inject optical pulses into receiver and measure independently with calibrated meter.
Optical Alignment (Instr. & S/C):
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Simulate lunar orbit signal conditions with changing return and background signals, verify false alarm rate using ranging performance
test data
Reflectivity Measurements (Instr):
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Provide simulated range returns via pulsed optical signals and CW background into each detector via fiber optic test port.
Verify boresight alignment at instrument assembly, before and after vibe and during TVAC
Measure LOLA optical axis wrt ref. cube on instr.
Measure LOLA ref. cube wrt S/C alignment cube after integration, vibe, TVAC and shipment to launch site
Laser Performance (Instr. & S/C):
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Continuous monitoring of laser output energy
Periodic measurement of beam quality (during alignment)
ANALYSES:
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Structural
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Thermal
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STOP (Structural-Thermal-Optical)
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Optical Stray Light
Analysis and Test result are assessed with respect to requirements for compliance
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Requirements tracking includes verification methods and compliance criteria
NASA’s Goddard Space Flight Center
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Instrument Current Status
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Major trade studies since Instrument inception which have been closed
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Major ongoing trade studies which could impact either Instrument top-level
requirements
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MEB coupling to Optic Deck
Laser Ranging for Orbit Determination
Analyses currently being performed:
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Oscillator Count and Location => LRO provides signal and reliability (mass savings)
Be vs. Aluminum => Be (mass savings)
BK7 vs Sapphire => BK7 (mass savings)
Interface comms =>1553 (flight experience)
Structural
Thermal
Reliability
Hardware currently in development:
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Laser
Electrical (Power, Analog, Digital)
NASA’s Goddard Space Flight Center
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LOLALOLA
Development
Schedule
Instrument Development
2005
Task
Q1
Q2
2006
Q3
Q4
Q1
Q2
2007
Q3
Q4
Q1
Q2
Q3
Q4
LOLA Project
SRR
PDR
D - PDR
CDR
PER
PSR
4/21
6/17
9/15
3/31
2/15
8/29
Instrument Reviews
Instrument Delivery
10/15
LOLA Design & Fabrication
Algorithm Doc.
Final Flight Parameters
FSW Test Report
Algorithms (Jan McGarry)
1/10
10/25
Laser Optical Design
Populate Laser Bench
Laser (Danny Krebs)
1/10
5/7
5/8
Prototypes Characterized
Beam Expander Integration
Optics (Luis Ramos)
4/11
PCA & LEA Req's
Det. Board Layout
1/24
Detector Board Integration
EM Test MEB FM MEB Vibe/TVAC
4/13
Electrical (Glenn Unger)
1/10
Low Fidelity Simulator
Software Release #2
Software Release #3
Software (J-P Swinski)
1/30
2/1
11/24
Prelim. Mech. Design
FM Det. Board Mech. ICD
FM Optical Bench
E-Box Test Fixtures
Mechanical (Steve Schmidt)
1/10
4/3
Detailed Thermal Model
Thermal Model Data
TVAC Test Plan
Final Thermal Analysis
Thermal (Carlton Peters)
1/10
9/4
BCE System Design
Laser BCE
BCE (Haris Riris)
4/29
5/24
Final Cal/Pre-ship Functional
Flight I&T (Michael Wright)
2/21
4/16
Instrument Ready for Delivery
8/30
8/30
30 Working Days
of Schedule Slack
Milestone
NASA’s Goddard Space Flight Center
Completed Milestone
Critical Path
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Summary
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Network Schedule Established
Grass-roots Budget Estimation In Process
Instrument Requirements Document Baselined
Constraints on LRO have been flowed down and captured in the MRD.
Breadboarding Successful
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Diffractive Optic Element (DOE)
Laser
Fiber optic alignment
SRR/PDR Completed, “Passed with Reservations”
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Delta-PDR required.
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Double check requirements flow-down to Level IV
Check readiness of subsystems for final design
Ready to move to preliminary design
NASA’s Goddard Space Flight Center
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