LEND Instrument Summary



CRaTER Pre-Environmental Review

Instrument Summary

The CRaTER instrument is located on the LRO science deck as shown in the figure below. A summary of key parameters for the instrument are included in the table below.

CRaTER Placement on the LRO Spacecraft

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Summary of CRaTER Parameters

|Mass Allocation |6.4 kg |

|Power Consumption Allocation |9.0 W |

|Size |13.5”x 9” x 6” |

|Function |Tissue equivalent response to radiation |

|Operational Temperature Range |-30о С to +30о С |

|Data Rate Allocation |89.1 Kbps |

The primary goal of CRaTER is to characterize the global lunar radiation environment and its biological impacts. In order to achieve this high-priority objective, the CRaTER investigation team established the following interrelated investigation goals:

1. Measure and characterize that aspect of the deep space radiation environment, linear energy transfer (LET) spectra of galactic and solar cosmic rays (particularly above 10 MeV), most critically important to the engineering and modeling communities to assure safe, long-term, human presence in space.

2. Develop a novel instrument, steeped in flight heritage, that is simple, compact, and comparatively low-cost, but with a sufficiently large geometric factor needed to measure LET spectra and its time variation, globally, in the lunar orbit.

3. Investigate the effects of shielding by measuring LET spectra behind different amounts and types of areal density, including tissue-equivalent plastic.

4. Test models of radiation effects and shielding by verifying/validating model predictions of LET spectra with LRO measurements, using high-quality Galactic Cosmic Ray (GCR) and Solar Proton Event (SPE) spectra available contemporaneously on ongoing/planned NASA.

The investigation hardware consists of a single, integrated sensor and electronics box with simple electronic and mechanical interfaces to the spacecraft. The CRaTER sensor front end design is based on standard stacked-detector, cosmic ray telescope systems that have been flown for decades, using detectors developed for other NASA flight programs. The analog electronics design is virtually identical to the robust and flight-proven design of the NASA/POLAR Imaging Proton Spectrometer that has been operating flawlessly on orbit since 1996. The digital processing unit is a simple and straightforward design also based on similar instruments with excellent spaceflight heritage. No new technology developments or supporting research are required for the final design, fabrication, and operation of this instrument.

The CRaTER telescope consists of six ion-implanted silicon detectors, mounted in pairs and separated by 2 cylinders of tissue-equivalent plastic (TEP). The detectors are all 35 mm in diameter. One of each pair is 140 microns thick; the other of each pair is 1000 microns thick.

CRaTER Assembly Layout

L13.5”x W9” x H 6”

Weight 6.4 kg max.

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CRaTER Theory of Operation

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Summary of Spacecraft Mechanical Requirements flowed to the CRaTER Instrument

(Excerpts from the LRO Mechanical Systems Specification, 431-SPEC-000012 Rev D)

Tailored Instrument Limit Loads (based on instrument location)

|Instrument |Limit Load |

| |(g, any direction) |

|CRaTER |8.0 |

|Diviner Instrument |8.0 |

|Diviner DREB |12.0 |

|LAMP |9.0 |

|LEND |8.0 |

|LOLA OTA |8.0 |

|LOLA MEB |9.0 |

|LROC NAC |8.0 |

|LROC WAC |9.0 |

|LROC SCS |8.5 |

|Mini-RF Antenna |12.0 |

|Mini-RF Electronics Boxes |12.0 |

CRATER Instrument X-Axis Sine Vibration Environment

|Protoflight/Qualification |Acceptance |

|Frequency (Hz) |Level |Frequency (Hz) |Level |

|5 - 9.9 |1.27 cm D.A. |5 - 8.8 |1.27 cm D.A. |

|9.9 - 50 |2.5 g’s |8.8 - 50 |2.0 g’s |

CRATER Instrument Y-Axis Sine Vibration Environment

|Protoflight/Qualification |Acceptance |

|Frequency (Hz) |Level |Frequency (Hz) |Level |

|5 - 15.6 |1.27 cm D.A. |5 - 14.0 |1.27 cm D.A. |

|15.6 - 25 |6.25 g’s |14.0 - 25 |5.0 g’s |

|25 - 50 |3.125 g’s |25 - 50 |2.5 g’s |

CRATER Instrument Z-Axis Sine Vibration Environment

|Protoflight/Qualification |Acceptance |

|Frequency (Hz) |Level |Frequency (Hz) |Level |

|5 - 17.1 |1.27 cm D.A. |5 - 15.3 |1.27 cm D.A. |

|17.1 - 25 |7.5 g’s |15.3 - 25 |6.0 g’s |

|25 - 50 |3.125 g’s |25 - 50 |2.5 g’s |

Generic Instrument Random Vibration Environment

|Frequency (Hz) |Protoflight/Qual Level |Acceptance Level |

|20 |0.026 g2/Hz |0.013 g2/Hz |

|20 - 50 |+6dB/Octave |+6dB/Octave |

|50 - 800 |0.160 g2/Hz |0.080 g2/Hz |

|800 - 2000 |-6dB/Octave |-6dB/Octave |

|2000 |0.026 g2/Hz |0.013 g2/Hz |

|Over All |14.1 grms |10.0 grms |

CRaTER shock response spectrum

|Frequency (Hz) |Level (Q=10) |

|100 |15 g |

|100 - 1000 |+9.3 dB/Octave |

|1000 - 10000 |525 g |

Summary of Spacecraft Thermal Requirements flowed to the CRATER Instrument

(Excerpts from the LRO Thermal Systems Specification, 431-SPEC-000091 Rev C)

Spacecraft Interface Temperature Range

|Subsystem |Component |Temperature Range ((C) |

| | |Op I/F Limit |Qual I/F Limit |Surv I/F Limit |

|CRATER |S/C at I/F to CRATER |-30 to +35 |-40 to +35 |-40 to +35 |

Temporal Gradient Requirements

|Subsystem |Component |Temporal Gradient ((C/min) |

|CRATER |S/C I/F to the Instrument |None |

Spatial Gradient Requirements

|Subsystem |Component |Spatial Gradient between mounting feet ((C) |

|CRATER |S/C I/F to the Instrument |None |

(Excerpts from the CRATER to Spacecraft Thermal ICD, 431-ICD-000119 Rev A)

CRATER Reference Location Temperature Limits

|# |Description |Node # |Min/Max Temp. Limits (°C) |

| | | |OPER. |SURV. |QUAL. |

LRO Thermal Design Drivers

(External environmental fluxes)

| | |

| | |

| | |

|( = 0( case (Noon Orbit, Hot Condition) | |

|Lunar IR environment - Temperature varies – 100 | |

|to 400 K (Subsolar point). | |

| | |

| | |

|View from Sun | |

| | |

| | |

|( = 90( case (Terminator Orbit, Cold Condition) | |

|Instrument exposed to full direct Solar flux | |

|Lunar IR (~ 150 K continuous) | |

| | |

Summary of Spacecraft Contamination Control Requirements flowed to the CRATER Instrument

(Excerpts from the LRO Contamination Control Plan, 431-PLAN-000110 Rev -)

Contamination Budget for LRO Instruments

|Instrument |Component |Delivery To LRO |

|CRaTER | ................
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