A--LUNAR RECONNAISSANCE ORBITER MISSION COMMUNICATION SYSTEM

LRO RF Communications Reference Baseline dated June 2, 2005 This document is intended to inform interested vendors of the current baseline architecture for the Lunar Reconnaissance Orbiter mission communication system. This document describes the current project understanding of LRO’s mission communications as a result of the project’s previous RFI process. This is not a request for additional RFI responses, nor is this a request for vendor proposals. No procurement action will be taken as a result of this document’s release. The LRO Project intends to initiate three separate competed procurement efforts to acquire the flight components for the LRO Spacecraft Communication System. These procurements will consist of the S-Band TT&C Transponder, the High-Rate Ka-Band Modulator, and the Ka-Band Traveling Wave Tube Amplifier (TWTA). LRO shall provide tracking, telemetry and command functions using S-Band. LRO shall provide high rate mission data return at Ka-band. At a minimum, LRO will perform a 30 minute TT&C pass every lunar orbit (approximately every 2 hours). LRO will perform up to 4 high rate Ka-band downlinks in a 24 hour period. The high rate downlinks may be adjacent passes. S-Band TT&C Subsystem LRO’s S-Band TT&C subsystem architecture consists of a STDN transponder and associated diplexer, switches and RF network to connect the transponder to the omnidirectional and high gain antennas. Command decryption (if required) can be accommodated internal to the transponder, or through the use of a standalone command decryptor in-line between the transponder receiver and the S-Band comm. card in the C&DH processor. The transponder shall provide the following modes: Transponder Characteristics: Downlink data: RS-422 CLK and DATA Uplink data: RS-422 CLK and DATA Control/Status: RS-422 serial UART interface RF Output: S-Band 5W Command Uplink (Ground to LRO) Frequency Band: 2.025 - 2.11 GHz Command Modulation: PCM/PSK/PM Command Subcarrier: 16 KHz Command Data Rate: 4 Kbps Command Link FEC: (none) Command Decryption: Caribou assumed Tracking: STDN tones, baseband modulated Simultaneous with CMD Highest ranging tone will be 500 KHz Telemetry Downlink (Subcarrier Modulated Mode) (LRO to Ground) Frequency Band: 2.2 – 2.29 GHz Telemetry Modulation: PCM/PSK/PM Telemetry Subcarrier: 1.024 MHz Telemetry Data Rates: 16Kbps (36.64 K-symbols/sec) 32Kbps (73.28 K-symbols/sec) 64Kbps (146.56 K-symbols/sec) 128Kbps (293.12 K-symbols/sec) Downlink FEC: CCSDS Reed-Solomon & Convolutional Rate ½ Downlink Encryption: (none) Tracking: STDN tones, baseband modulated Simultaneous with TLM Highest ranging tone will be 500 KHz Telemetry Downlink (Direct Modulated Mode) (LRO to Ground) Frequency Band: 2.2 – 2.29 GHz Telemetry Modulation: OQPSK (direct carrier) Telemetry Subcarrier: (none) Telemetry Data Rates: 300Kbps (687 K-symbols/sec) 2180Kbps (4992.2 K-symbols/sec) 5000Kbps (no FEC) Downlink FEC: CCSDS Reed-Solomon & Rate ½ (2.29x multiplier) Downlink Encryption: (none) Tracking: (none) Ka-Band Mission Data Subsystem LRO’s Ka-band subsystem consists of a high rate Ka-band modulator, TWTA, EPC, and the RF network between the TWTA and LRO’s high gain antenna. Modulator Characteristics: Downlink Data: LVDS CLK and DATA Control/Status: RS-422 serial UART interface RF Output: +7 dBm (at the modulator output port) TWTA/EPC Characteristics: Control/Status: Discrete RF Output: Ka-Band 20W (+13 dBW) RF Input: >0 dBm (at the TWT input port) High Rate Data Downlink (LRO to Ground) Frequency Band: 25.5 – 27.0 GHz Telemetry Modulation: OQPSK (direct carrier) Telemetry Subcarrier: (none) Telemetry Data Rates: 25Mbps (57.25 M-symbols/sec) 50Mbps (114.5 M-symbols/sec) 100Mbps (229 M-symbols/sec) Downlink FEC: CCSDS Reed-Solomon & Rate ½ (2.29x multiplier) Downlink Encryption: (none) Tracking: (none)