10 - 1 LRO System Requirements Review Lunar Exploration Neutron Detector (LEND) Requirements &...

10 - 1

LRO System Requirements ReviewLunar Exploration Neutron Detector (LEND)

Requirements & Implementation

Igor MitrofanovPrinciple Investigator

Russian Institute for Space Research

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Institutions of LEND Instrument Team

Computer Science Corporation, USA

Catholic University of America, USA

University of Arizona, USA

NASA/Goddard Space Flight Center, USA

University of Maryland, USA

Joint Institute of Nuclear Research, Russia

Sternberg Institute of Astronomy, Russia

Institute for Space Research, Russia

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SETN

STN 2

STN 3

STN 1

LEND sensors of STN1-3 and SETN detect thermal neutrons and epithermal neutrons to characterize Lunar Radiation Environment.

STN1 and STN3 operates as Doppler filter for thermal neutrons from front side and back side of LEND

SETN and STN2 have open fields of view

LRO velocity vector

LEND Science Overview and Theory of Operations

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SHEN

LEND sensor SHEN detects high energy neutrons at 16 energy channels from 300 keV to >15 MeV to characterize Lunar Radiation Environment

SHEN has narrow field of view about 20-30


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CSHEN 1

LEND collimated sensors CSETN1-4 detect epithermal neutrons with high angular resolution to characterize spatial variations of Lunar Neutron Albedo, which depend on content of hydrogen in 1-2 m of the regolith

CSHEN 2

CSHEN 3

epithermal neutrons


H

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CSHEN 1

LEND collimated sensors CSETN1-4 and SHEN detect epithermal neutrons and high energy neutrons with high angular resolution to test water ice deposit on the surface

CSHEN 2

CSHEN 3

epithermal neutrons


high energy neutrons

SHEN

water ice

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HEND/Odyssey is LEND prototype with few design changes

Plastic Anti-coincidence for Sensor of HEN

Collimator of neutrons

Larger counters of neutrons

LEND Heritage

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LEND electronics has only one design change in respect to HEND

Design Change

LEND Heritage

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Project:

LRO Program Requirements Document; ESMD-RLEP-0010LRO Mission Requirements Document; 431-RQMT-00004 LRO Technical Resource Allocations; 431-RQMT-000112

Instrument:

Instrument Payload Assurance Implementation Plan LEND PAIP 01Instrument to Spacecraft Interface Control Documents

Mechanical 431-ICD-000088Thermal 431-ICD-000119Electrical 431-ICD-000097Data 431-ICD-000107

Instrument Requirements Document LEND IRD 01

Contract documents with Russian Federal Space Agency

Draft of LEND Implementation Agreement between NASA and FSA

LEND Documentation

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LRO

Req.Level 1: Requirements

ESMD-RLEP-0010

InstrumentLRO Mission

Requirement

Required Data Products (LEND Level 3 and 4)

RLEP-LRO-M110

LEND The LRO shall map hydrogen on the Moon's surface with 5 km spatial resolution at the poles for concentrations equal or greater than 100 ppm with 3-sigma confidence.

The LRO shall obtain high spatial resolution hydrogen mapping of the Moon's surface to a 20% accuracy and 5 km resolution at the poles.

LEND Surface Composition Data Product (LEND SCDP):

LEND SCDP#1: Map of hydrogen composition with pixels of 2 km for northern area >60N LEND SCDP#2: Map of hydrogen composition with pixels of 2 km for southern area >60S LEND SCDP#3: Map of hydrogen composition with pixels of 5-10 km for equatorial belt between >60N and >60SDetermine hydrogen content of subsurface at polar regions with spatial resolution from Half-Width Half-Maximum (HWHM)=5km and with variation sensitivity from 100 parts per million (ppm)

RLEP-LRO-M070

LEND The LRO shall identify putative deposits of appreciable surface or near surface water ice in the Moon’s polar cold traps at km’s 100m scale spatial resolution


LEND SCDP#4: Map of water ice deposits with pixels of 2 km for northern area >60N LEND SCDP#5: Map of water ice deposits with pixels of 2 km for southern area >60SDevelop maps of water ice column density on polar regions of the Moon with spatial resolution from 5-20km.

RLEP-LRO-M010

LEND The LRO shall characterize the deep space radiation environment in lunar orbit, including neutron albedo.

LEND Radiation Data Products (LEND RDP):

LEND RDP #1: Maps of thermal neutrons below 0.4 eV, epithermal neutrons at two energy ranges (0.4 eV – 3.0 keV) and (3 – 300 ) keV and maps of high energy neutrons at 16 energy channels from 300 keV up to 15 MeV for 52 time periods of 7 days

LEND RDP #2: Time profiles of thermal neutrons below 0.4 eV, epithermal neutrons at two energy ranges (0.4 eV – 3.0 keV) and (3 – 300 ) keV and maps of high energy neutrons at 16 energy channels from 300 keV up to 15 MeV for each detected SPE

LEND RDP #3 (optional, provided LEND-LRO R3# accepted): Angular distribution of epithermal and high energy neutron components of lunar space radiation environment from Nadir to Horizon at 15 steps

Radiation Data Product for global distribution of neutrons at Moon’s orbit with spatial resolution of 50 km at different energy ranges from thermal energy up to >15 MeV separately for periods of quiet Sun and for periods of Solar Particle Events.

LEND Mission Level Requirements

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Level 1 Req.

Instrument Level 2 Requirements

(LEND IRD 01) Concept/Realizability

/Comment

Requirement no.

LEND Instrument Measurement Requirement

M 110-LEND LEND IMR 1 Measure global distribution of hydrogen in lunar subsurface; at polar regions provide spatial resolution from 5 km (Half-Width Half-Maximum, HWHM) and variation sensitivity with confident detection limit of 100 weight parts per million (ppm)

Determine hydrogen content of subsurface at polar regions with spatial resolution from Half-Width Half-Maximum (HWHM)=5km and with variation sensitivity from 100 parts per million (ppm)

LEND has imaging capability for lunar flux of epithermal neutrons (collimated sensors CSETN 1-4), which variations are the most pronounced signature of hydrogen content in the subsurface layer of 1-2 meters

M 070-LEND LEND IMR 2 Measure or estimate upper limit of water ice column density on polar regions of the Moon with spatial resolution of 5-20 km

Develop maps of water ice column density on polar regions of the Moon with spatial resolution from 5-20km.

LEND has imaging capability for lunar flux of epithermal neutrons (collimated sensors CSETN 1-4) and high energy neutrons (sensor SHEN): relationship of variations of these neutrons provides the signature of water ice deposits on polar regions of Mars

M 10-LEND LEND IMR 3 Measure global distribution of neutrons at Moon’s orbit with spatial resolution of 50 km at different energy ranges from thermal energy to >15 MeV separately for periods of quiet Sun and for periods of Solar Particle Events

Radiation Data Product for global distribution of neutrons at Moon’s orbit with spatial resolution of 50 km at different energy ranges from thermal energy up to >15 MeV separately for periods of quiet Sun and for periods of Solar Particle Events.

LEND has the necessary-and-sufficient set of sensors for entire energy range from thermal energy domain to 15 MeV and higher, which allow to build up comprehensive physical model of neutron component of radiation environment both for quiet Sun period and for episodes of SPE

LEND Instrument System Level Requirements

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Level 2 Req.

Instrument Level 2a Requirements

(LEND IRD 01) Concept/Realizability/Comment

Requirement no.

LEND Instrument Functional Requirement

LEND

IMR 1

LEND FR 1 Measure epithermal neutrons by 4 similar collimated sensors with counting rate about 0.3 counts/sec within narrow FOV, which allows to detect polar spot with 100 ppm of hydrogen and radius of 5 km at 3-sigma confidence

Narrow FOV of CSETN 1-4 is produced by passive collimator module from 10BC4 and polyethylene; realizability to be proved by Monte Carlo numerical modeling and physical tests of laboratory prototype unit

LEND

IMR 2

LEND FR 2 Measure high energy neutrons by narrow field sensor at 16 energy channels from 300 keV to > 15 MeV

SHEN has plastic anti-coincidence shield to reject counts from charge particles; narrow field of view is produced by center hole of collimator module for counters CSETN 1-4 (*.

Joint analysis of data from CSETN 1-4 (FR 1) and from scintillator SHEN (FR 2) allows to detect layering structure of water ice deposits

LEND

IMR 3

LEND FR 2 See above See above (*

LEND FR 3 Measure thermal neutrons by two Doppler-filter sensors

Signal of Doppler filter, which is subtraction of counts of front side counter STN 1 from counts of back side counter STN 3, exclude local background of spacecraft

LEND FR 4 Measure thermal neutrons by open-field sensor Counter SETN has Cd enclosure and its counts rate characterizes total flux of epithermal neutrons at the orbit. Difference of counts from STN 2 and SETN characterizes total flux of thermal neutrons at the orbit LEND FR 5 Measure epithermal neutrons by open field sensor


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Level 2 Req.


(LEND IRD 01) Concept/Realizability

/Comment

Requirement no.

LEND Instrument Design Requirement

LEND FR 1

L3-DR 01 Measure epithermal neutrons with counting rate about 0.3 counts/sec inside FOV of about 5.6 at each collimated counter CSETN 1-4

Monte Carlo simulations show that optimal design of collimator together with appropriate selection of 3He counter of neutrons allow to obtain necessary counting rate for SETN 1-4 sensors within allocated mass (see backup page TBD). Selected prototype for counters is LND 25311.

LEND FR 3, 4 and 5

L3-DR 02 Measure thermal and epithermal neutrons in CTN 1-3 and SETN with counting rate about 10 cts/sec

Monte Carlo simulation of lunar neutron albedo allows to select necessary type of 3He counters for STN 1-3 and SETN for getting this counting rate. Selected prototype for counters is LND 25311.

LEND FR

1, 3-5

L3-DR 03 Provide signal processing from counters CSETN 1-4, STN 1-3 and SETN

Each signal will be digitized in 16 channels of amplitude and loaded into corresponding place of LEND telemetry frame (HEND heritage)

L3-DR 04 Provide changeable HV about 2 kV for counters CSETN 1-4, STN 1-3 and SETN

Turn on/off and Levels of HV may be operated individually for each counter (HEND heritage)


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Level 2 Req.


(LEND IRD 01) Concept/Realizability/Comment

Requirement no. or para.

LEND Instrument Design Requirement

LEND FR 2 L3-DR 05 Provide changeable HV about 2 kV for PMT of SHEN

HEND heritage

L3-DR 06 Distinguish SHEN counts from neutrons and counts from gamma-rays

Pulse-shape analyzer will be used for signal from PMT, which allows to separate counts from proton (detection of neutron) from electron (detection of gamma-ray) with probability of mistake less than 10-3 (HEND heritage)

L3-DR 07 Measure high energy neutrons at the energy range (300 keV, >15 MeV) with counting rate about 0.3 cts/sec

Monte Carlo simulation of lunar neutron albedo allows to select size of sthylbene scintillation sensor SETN for getting this counting rate within narrow FOV (HEND heritage).

L3-DR 08 Provide 2 signals (neutrons and gammas) processing in 16 energy channels

Each signal will be digitized in 16 channels of amplitude and loaded into corresponding place of LEND telemetry frame (HEND heritage)

L3-DR 09 Provide anti-coincidence shielding for SHEN for exclusion detection of external charge particles

Sthylbene crystal will be surrounded by plastic scintillator with photo-diodes read-out, which generates veto anti-coincidence signal for each crossing charge particle (HEND heritage)


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LEND Data

Description Required Input

LEND Level 0

Unprocessed LEND rough telemetry data with science measurements, instrument housekeeping information. Spacecraft LEND-related data

Spacecraft LEND-related data

LEND Level 1

LEND sensors counting rate, LEND physical calibration data, spacecraft trajectory and pointing data, LEND sensors counting rate from background, solar activity data

Spacecraft timing, trajectory and pointing data, spacecraft data for fuel consumption, CRaTER level TBD data, GOES solar data

LEND level 2

LEND neutron mapping data (flux of neutrons per pixel) and/or time profiles with integration time and pixelization individually selected for each sensor

LOLA level TBD data, Diviner level TBD data

LEND level 3


LEND SCDP#1: Map of hydrogen composition with pixels of 2 km for northern area >60N LEND SCDP#2: Map of hydrogen composition with pixels of 2 km for southern area >60S LEND SCDP#3: Map of hydrogen composition with pixels of 5-10 km for equatorial belt between 60N and 60S LEND SCDP #4: Map of water ice deposits with pixels of 2 km at northern area > 80N LEND SCDP #5: Map of water ice deposits with pixels of 2 km at southern area > 80S

LOLA level TBD data, Diviner level TBD data, LAMP level TBD data

LEND level 4

LEND Radiation Data Products (LEND RDP):

LEND RDP #1: Maps of thermal neutrons below 0.4 eV, epithermal neutrons at two energy ranges (0.4 eV – 3.0 keV) and (3 – 300 ) keV and maps of high energy neutrons at 16 energy channels from 300 keV up to 15 MeV for 52 time periods of 7 days

LEND RDP #2: Time profiles of thermal neutrons below 0.4 eV, epithermal neutrons at two energy ranges (0.4 eV – 3.0 keV) and (3 – 300 ) keV and maps of high energy neutrons at 16 energy channels from 300 keV up to 15 MeV for each detected SPE

CRaTER level TBD data

LEND Data Product Traceability

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RLEP-LRO Requirement LEND measurement requirements LRO requirement driven by LEND

RLEP-LRO-M110: The LRO shall map hydrogen on the Moon's surface with 5 km spatial resolution at the poles for concentrations equal or greater than 100 ppm with 3-sigma confidence.

LEND IMR 1: Measure global distribution of hydrogen in lunar subsurface; at polar regions provide spatial resolution from 5 km (Half-Width Half-Maximum, HWHM) and variation sensitivity with confident detection limit of 100 weight parts per million (ppm)

LEND-LRO R#1: For neutron mapping measurements provide continuously pointing of LEND collimated detectors into nadir direction

RLEP-LRO-M70: The LRO shall identify putative deposits of appreciable surface or near surface water ice in the Moon’s polar cold traps at km’s scale spatial resolution

LEND IMR 2: Measure or estimate upper limit of water ice column density on polar regions of the Moon with spatial resolution of 5-20 km

The same LEND-LRO R#1 (see above)

RLEP-LRO-M10: The LRO shall characterize the deep space radiation environment in lunar orbit, including neutron albedo.

LEND IMR 2: Measure global distribution of neutrons at Moon’s orbit with spatial resolution of 50 km at different energy ranges from thermal energy to >15 MeV separately for periods of quiet Sun and for periods of Solar Particle Events

The same LEND-LRO R#1 (see above)

LEND-LRO R#2: Operate LEND constantly from cruise orbit insertion during the entire mission

LEND-LRO R#3: Provide opportunity for sessions of special measurements with different angles of collimated detectors from Nadir to Horizon (suggested, as optional. in addition to baseline mission scenario, provides additional LEND Data Product LEND RDP #3)

LRO Requirements Driven by LEND

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LEND 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 LOLA’s 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)

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LEND Instrument

Main Structure

STN2/FRE

Sensor SETN

Sensor STN1

Sensor STN2

HV1

HV2

HV3

Stil-bene

Sensor SC/N

Sensor SC/AC

SC/N/FRE&S

SC/AC/FRE

SC/N/SA4

Actel FPGA (RTAX series)

Neutron Energy Code

G/N

N/G

Block

HV9

HV/STN/

CSETN

High VoltagesValues

HV6HV7HV8HV9

ACS

STN1/FRE

SETN/FRE

LVP

TCS

IC

IO Drivers

RAM ClockGenerator

LEND

CSETN2/FRE

Sensor STN3

Sensor CSETN1

Sensor CSETN2

HV4

HV5

HV6

CSETN1/FRE

STN3/FRE

CSETN4/FRE

Sensor CSETN4

HV7

HV8

CSETN3/FRE

Sensor CSETN3

HV1HV2

HV4HV5

HV3

ADC

LRO

Spacecraft

Redundant MIL-STD-1553B

HeatersControl

LEND Block Diagram

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LEND units

Sta

ge

s o

f L

EN

D d

ev

elo

pm

en

t

Fu

nc

tio

na

l R

eq

.D

es

ign

Re

q.

LR

O E

nv

. R

eq

.L

RO

In

teg

rati

on

LEND LU LEND QU LEND FU01 LEND FU02LEND EU

Laboratory testswith neutron sourcesand numerical simulations

Laboratory testswith neutron sources, verification tests for LRO environment requirements

Qualification tests for LRO environment requirements

Acceptance tests for LRO environment requirements

Integration tests onboard LRO

LEND Development Flow

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• Reliability Analyses (RA)• Failure Modes, Effects and Criticality Analysis (FMECA)• Electronic Parts Stress Analysis (PSA)• Thermal Stress Analysis• Structural Stress Analysis• Single Event Effects Analysis (SEE)

• Screening of all electrical, electronic and electromechanical parts (SEEE)• Preparation of Confirmation Lists of Material and Components (CLMC)• Environmental Requirements (ER)

• Radiation durability analysis• Random vibration and shock tests• Thermal vacuum test• Electromagnetic compatibility tests• Thermal cycling life test

• Contamination Control (CC)• Preparation of Problem/Failure Anomaly Report (PFAR)• Accumulation of Hardware Operating Hours prior delivery (HO)

List of Procedures and Verification Tests

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•Trade studies which have been closed• Concept of LEND configuration• Electrical interface design• Selection of sensors and major electronic components• Concept of thermal design• Concept of mechanical design• Manufacturing documentation for LEND LU• Cooperation in Russia for LEND manufacturing

•Outgoing trade studies• Optimization of collimator unit of SETN 1-4 for the best sensitivity for 5 km radius spot at pole with enhancement of H• Optimization of narrow field of view for detector of high energy neutrons SHEN • Thermal model of instrument

•Analysis currently being performed• Numerical model of Moon neutron albedo at different energy ranges• Estimation of instrument fundamental frequency ( > 75 Hz)• Software for data processing of LEND LU

•Hardware currently in development• Mechanical elements of LEND LU• Collimator units of LEND LU• Electronic boards of LEND LU

7. What is the status of the agreements?

LEND Current Status

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Name Work 2004 2005 2006 2007 2008

LU Development

Testing&verification

EIS Development


Delivery

EU Development


Delivery

QU Development


Calibrations

FU01 Development


Calibrations

Delivery

FU02 Development


Calibrations

Delivery

LEND Development Milestones

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1. LEND is developing in response to RLEP-LRO M010, M070 and M110: corresponding flowsfrom LRO Mission requirements to LEND Functional Requirements and Design Requirements arewell understood

2. Data Products of LEND are defined, which correspond to RLEP-LRO M010, M070 and M110

3. LEND development process ensures that LEND Flight Unit will provide defined Data Products

4. LEND accommodation on LRO ensures that LEND will be able to provide defined Data Products

5. There is only one additional requirement to LRO driven by LEND (measurements at different angles from Nadir to Horizon) which is not presented in the mission baseline. This operation provides additional data products on Lunar Radiation Environment (angular distribution ofneutron component)

6. LEND team is ready to move to the preliminary design stage

7. What is the status of the agreements?

Summary

10 - 1 LRO System Requirements Review Lunar Exploration Neutron Detector (LEND) Requirements &...

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