Spacecraft Thermal System Charles Baker Code 545 August 16-17, 2005

Level 1 - LRO Requirements ESMD-RLEP-0010 Lunar Reconnaissance Orbiter (LRO) Thermal Level System Requirements Traceability Level 1 - LRO Requirements ESMD-RLEP-0010 Level 2 - LRO Mission Requirements Document 431-RQMT-000004 LRO Technical Resource Allocations 431-SPEC-000112 LRO Electrical Systems Specification 431-SPEC-000008 LRO Thermal Systems Specification 431-SPEC-000091 LRO Mission Concept of Operations 431-OPS-000042 LRO Pointing and Alignment Specification 431-SPEC-000113 Level 3 - LRO Thermal Math Model Specification 431-SPEC-000092 LROC Thermal Interface Control Document 431-ICD-000114 LAMP Thermal Interface Control Document 431-ICD-000115 Diviner Thermal Interface Control Document 431-ICD-000116 LOLA Thermal Interface Control Document 431-ICD-000117 CRaTER Thermal Interface Control Document 431-ICD-000118 LEND Thermal Interface Control Document 431-ICD-000119 Mini-RF Thermal Interface Control Document 431-ICD-000159

Lunar Reconnaissance Orbiter (LRO) Thermal System Level 2 Flow Down Key Requirements Level 2 Req. Level 3: Requirements Concept/Compliance Paragraph Requirement MRD-78 Thermal Operational Ranges 431-SPEC-000091, Section 2.3 LRO’s Thermal Control System shall be designed, analyzed, and tested to demonstrate that operational temperature Interface requirements are met during the mission life. Convert mechanical design into a thermal design. Apply conservative assumptions to bounding operational cases per 431-SPEC-000091. Test worst cases in the T-Vac chamber simulating the lunar environment per 431-SPEC-000091. Thermal Cycle Qualification to show lifetime in accordance with GEVS. MRD-79 Thermal Survival Ranges LRO’s Thermal Control System shall be designed, analyzed, and tested to demonstrate that survival temperature Interface requirements are met during the mission life. Develop thermal models from mechanical design. Apply conservative assumptions to bounding survival cases per 431-SPEC-000091. Test worst cases in the T-Vac chamber. Thermally demonstrate survival in accordance with GEVS. MRD-31 Power Allocations 431-SPEC-000091, Section 3.2 LRO Thermal’s Heater circuits shall not exceed the allocations shown in Power Allocations Document 431-RQMT-000112. Individually predict heater power required for each heater location and sum the power consumed by each circuit in 431-SPEC-000091. MRD-4 Launch Window MRD-50 Mission Phases MRD-52 Sun Avoidance MRD-100 Thermal Off-Nominal Ops 431-OPS-000042 LRO Thermal shall be designed, analyzed, and tested per bounding thermal cases outlined in LRO Mission Operations Concept Document 431-OPS-000042 which will be broken into thermal assumptions in 431-SPEC-000091. The thermal design shall keep all temperatures in limits and not exceed heater power allocation in all attitudes that LRO is baselined to fly in.

Lunar Reconnaissance Orbiter (LRO) Thermal System Level 2 Flow Down Key Requirements Level 2 Req. Level 3: Requirements Concept/Compliance Paragraph Requirement MRD-21 Mission Duration 431-SPEC-000091, Section 5.2, 5.4 LRO’s Thermal Control System shall meet performance requirements for the full 14 month duration of the mission. Conservatively degrade thermal coatings to reflect environment driven degradations. Only use thermal component parts that are compliant with the mission lifetime. MRD-19 Lunar Eclipses MRD-20 Spacecraft Safing 431-SPEC-000091, Section 5.4 LRO thermal system shall be designed to maintain all components within the appropriate temperature limits during the lunar eclipse and during spacecraft safing. LRO thermal system will not exceed the lunar eclipse and safing heater power allocation. Operational and survival heaters will be sized by analysis and proved in test as having sufficient heater power at minimum voltages with GEVS margin to maintain all components within their appropriate temperature ranges during the lunar eclipse and safing periods. MRD-28 Vehicle Interfaces LRO thermal design shall be capable of maintaining all components within the appropriate temperature limits from Launch thru Separation including soak back from the third stage. Pre-separation thermal analysis shall be conducted. Of particular concern is the soak back from the third stage solid rocket motor MRD-6 Thermal Environments 431-SPEC-000091, Section 5.1 All thermal control systems (TCSs) shall be designed with conservative assumptions about the lunar environment biased hot and cold as outlined in 431-SPEC-000091. 431-SPEC-000091 defines the Solar Constant, lunar infared radiation, Lunar albedo per orbit location and Beta angle. TSS will be used to predict imposed environmental fluxes.

Lunar Reconnaissance Orbiter (LRO) Thermal System Level 2 Flow Down Key Requirements Level 2 Req. Level 3: Requirements Concept/Compliance Paragraph Requirement MRD-70 Structural Stability 431-SPEC-000113 431-SPEC-000091, Section 2.4, 2.5 The LRO thermal system shall predict temperatures on the spacecraft structure. The thermal predicts will be mapped onto the mechanical FEM model for subsequent use in STOP analyses. The thermal induced distortions shall be mechanically/thermally designed to stay within the mission pointing budgets. Spatial and temporal thermal gradients requirements shall be captured in 431-SPEC-000091 and verified thru analysis and test. Perform a STOP analysis. Evaluate thermal gradients thru TSS/SINDA models, modify the thermal/mechanical design to meet the requirements MRD-81 Monitoring 431-SPEC-000091, Section 2.7 The LRO thermal system shall identify locations for S/C monitored temperature sensors at thermal interfaces. Components and Instruments shall identify locations for S/C monitored temperature sensors within components. Allocations of temperature sensors shall be provided in 431-SPEC-000091. Baseline is to provide two (2) temperature sensors per instrument/component.

Lunar Reconnaissance Orbiter (LRO) Temperature Requirements SUBSYSTEM COMPONENT TEMPERATURE RANGE (°C) Operational Survival Mechanical Structure Propulsion Module +70 to -50 +80 to -60 Structure -Avionics Module +50 to -50 +60 to -60 Structure -Avionics to Propulsion Structure. Instrument Module Fasteners +90 to -65 Mechanisms High Gain Antenna (HGA) Gimbals -10 to +50 -20 to +60 HGA Boom HGA Release and Deploy Solar Array (S/A) Gimbals S/A Boom S/A Release and Deploy Power Power Subsystem Electronics (PSE) -10 to 40 -20 to 50 Battery 10 to 30 0 to 40 S/A Cells/Cover Glass +130 (operating), +140 (non-operating) to -170 +140 to -175 S/A Substrate

Lunar Reconnaissance Orbiter (LRO) Temperature Requirements SUBSYSTEM COMPONENT TEMPERATURE RANGE (°C) Operational Survival Attitude Control System (ACS) Star Trackers -30 to +50 -30 to +60 Inertial Measurement Unit -30 to +65 -30 to +75 Reaction Wheels -10 to +50 Coarse Sun Sensors -120 to +80 -130 to +90 Propulsion and Deployables Electronics (PDE) Box and MTG Hardware -10 to +40 -20 to +50 Propulsion (Dry Mass) Hydrazine Tank 1 +10 to 40 N/A Pressure Tanks (Comment) +0 to 50 90N Thrusters 22N Thrusters High Press Transducers Low Press Transducer Gas Latch Valve Liquid Latch Valve Fill and Drain Gas System Filters Liquid Filters Pressure Regulators Plumbing Lines NC Pyro Valves, Pressurant

Lunar Reconnaissance Orbiter (LRO) Temperature Requirements SUBSYSTEM COMPONENT TEMPERATURE RANGE (°C) Operational Survival C&DH Box and Mounting Hardware -10 to 40 -20 to 50 S Comm -10 to +40 TT&C Omni Antenna -120 to +80 -130 to +90 Ka Comm Ka Baseband Modulator -10 to +50 -20 to 60 Ka TWTA w/EPC HGA +145 to -140 Cosmic Ray Telescope of the Effects of Radiation (CRaTER) S/C at I/F to CRaTER -30 to +35 -40 to +50 Diviner S/C at I/F to Diviner Instr -50 to +50 -60 to +60 S/C at I/F to remote electronics box -20 to +50 -70 to +80 Lyman-Alpha Mapping Project (LAMP) S/C at I/F to LAMP Lunar Exploration Neutron Detector (LEND) S/C at I/F to LEND -30 to +40 Lunar Orbiter Laser Altimeter (LOLA) S/C at I/F to Optics Assembly S/C at I/F to Main Electronics Box Lunar Reconnaissance Orbiter Camera (LROC) S/C at I/F to NACS S/C at I/F to WACS S/C at I/F to SCS Mini RF S/C at I/F to Antennae S/C at I/F to Electronics Package

Thermal Block Diagram – Instrument Module Zenith (Radiator Direction) LOLA MEB Star Cams LROC IMU Diviner REB CRaTER LEND LOLA Op Bench Thermal Isolation Nadir Anti-Sun (Radiator Direction) Instr Optical Bench Concept: Use zenith facing or anti-sun facing honeycomb panels that are cold biased and use heaters and thermostats to control the temperature

Thermal Block Diagram - Avionics Gimbal Cntrls Zenith (Radiator Direction) TWTA C&DH PSE S-Band Battery PDE LAMP Anti-Sun (Radiator Direction) Mini-RF Electronics Nadir Mini-RF Antennae Solar Array (shown in Beta 90°) Diviner Concept: Use zenith facing or anti-sun facing honeycomb panels that are cold biased and use heaters and thermostats to control the temperature

Thermal Block Diagram - Propulsion Conductive and Radiative Coupling to the Avionics 5# thrusters (8) RWAs 20# thrusters (2) Main Tank Pressurant Tank Concept: Use RWAs and Avionics module to keep propulsion system warm. Isolate from the third stage and thrusters.

Lunar Reconnaissance Orbiter (LRO) Thermal Verification Summary Analysis Predict Control Heater Power, Temperatures, Gradients of all thermal I/Fs during all bounding mission modes Provide inputs to STOP analysis Design Orbiter Thermal Vacuum test to provide GEVS qualification Component Tests All avionics boxes will be thermal cycled (8) All instruments with be thermal cycled (8) and thermal balanced Propulsion Module will be thermal cycled (8) and thermal balanced No thermal components will be component level tested since all thermal components (MLI, T-Stats, Film Heaters, Thermistors are previously space flight qualified) Orbiter Tests 2 Cold Startups, 2 Hot Startups Orbiter with be thermal cycled (4) and thermal balanced

Lunar Reconnaissance Orbiter (LRO) Thermal Requirements Summary The thermal group has been working closely with systems to understand and define the mission requirements that drive thermal Thermal is a back loaded subsystem, but preliminary analyses of the orbiter concept shows the design is feasible Thermal has established and is carrying sufficient margins to accommodate system changes on the road to CDR - system is robust Thermal is ready to proceed to PDR