Peter Ilott

Telecommunications relay support of the Mars Phoenix Lander mission

The Phoenix Lander, first of NASAs Mars Scout missions, arrived at the Red Planet on May 25, 2008. From the moment the lander separated from its interplanetary cruise stage shortly before entry, the spacecraft could no longer communicate directly with Earth, and was instead entirely dependent on UHF relay communications via an international network of orbiting Mars spacecraft, including NASAs 2001 Mars Odyssey (ODY) and Mars Reconnaissance Orbiter (MRO) spacecraft, as well as ESAs Mars Express (MEX) spacecraft. All three orbiters captured critical event telemetry and/or tracking data during Phoenix entry, descent and landing. During the Phoenix surface mission, ODY and MRO provided command and telemetry services, far surpassing the original data return requirements. The availability of MEX as a backup relay asset enhanced the robustness of the overall relay plan. In addition to telecommunications services, Doppler tracking observables acquired on the UHF link yielded a highly accurate position for the Phoenix landing site.12

Development and flight performance of CCSDS Proximity-1 on Odyssey and the Mars exploration rovers

The UHF relay link through the Mars Odyssey orbiter exceeded expectations of the Mars exploration rover (MER) project and played a critical role in the return of data from the surface of Mars and in the accuracy of the rover position determination. This paper will discus the development and performance of the UHF transceivers and the Consultative Committee for Spacecraft Data Systems (CCSDS) Proximity-1 space link protocol that were used by Odyssey and the two MER rovers; and some of the more prominent lessons learned during development and operations of the MER-Odyssey relay link

Relay support for the Mars Science Laboratory mission

The Mars Science Laboratory (MSL) mission landed the Curiosity Rover on the surface of Mars on August 6, 2012, beginning a one-Martian-year primary science mission. An international network of Mars relay orbiters, including NASAs 2001 Mars Odyssey Orbiter (ODY) and Mars Reconnaissance Orbiter (MRO), and ESAs Mars Express Orbiter (MEX), were positioned to provide critical event coverage of MSLs Entry, Descent, and Landing (EDL). The EDL communication plan took advantage of unique and complementary capabilities of each orbiter to provide robust information capture during this critical event while also providing low-latency information during the landing. Once on the surface, ODY and MRO have provided effectively all of Curiositys data return from the Martian surface. The link from Curiosity to MRO incorporates a number of new features enabled by the Electra and Electra-Lite software-defined radios on MRO and Curiosity, respectively. Specifically, the Curiosity-MRO link has for the first time on Mars relay links utilized frequency-agile operations, data rates up to 2.048 Mb/s, suppressed carrier modulation, and a new Adaptive Data Rate algorithm in which the return link data rate is optimally varied throughout the relay pass based on the actual observed link channel characteristics. In addition to the baseline surface relay support by ODY and MRO, the MEX relay service has been verified in several successful surface relay passes, and MEX now stands ready to provide backup relay support should NASAs orbiters become unavailable for some period of time.

MRO relay telecom support of Mars Science Laboratory surface operations

The Mars Science Laboratory (MSL) mission landed the Curiosity Rover on the surface of Mars on August 6, 2012, beginning a one Martian year primary science mission. The UHF relay link from Curiosity to the Mars Reconnaissance Orbiter (MRO) incorporates new features enabled by the Electra and Electra-Lite software-defined radios on MRO and Curiosity, respectively. Specifically, the Curiosity-MRO link has for the first time utilized frequency-agile operations, increased data rates from 256 kbps up to 2048 kbps, employed suppressed carrier modulation and a new Adaptive Data Rate algorithm in which the return-link data rate is varied to match the observed channel condition. During the first 200 sols, the telecom operations team has been able to tune the radio and protocol parameters to maximize return-link data volume, which is now averaging roughly 500 Mbits per sol or twice the design requirement of 250 Mbits per sol. The telecom team has also derived new predict models that reduce data volume prediction errors and that quantify the impact of operational modes and link parameters, providing further planning insight for MSL mission operations team.

Direct-to-Earth communications with Mars Science Laboratory during Entry, Descent, and Landing

Mars Science Laboratory (MSL) undergoes extreme heating and acceleration during Entry, Descent, and Landing (EDL) on Mars. Unknown dynamics lead to large Doppler shifts, making communication challenging. During EDL, a special form of Multiple Frequency Shift Keying (MFSK) communication is used for Direct-To-Earth (DTE) communication. The X-band signal is received by the Deep Space Network (DSN) at the Canberra Deep Space Communication complex, then down-converted, digitized, and recorded by open-loop Radio Science Receivers (RSR), and decoded in real-time by the EDL Data Analysis (EDA) System. The EDA uses lock states with configurable Fast Fourier Transforms to acquire and track the signal. RSR configuration and channel allocation is shown. Testing prior to EDL is discussed including software simulations, test bed runs with MSL flight hardware, and the in-flight end-to-end test. EDA configuration parameters and signal dynamics during pre-entry, entry, and parachute deployment are analyzed. RSR and EDA performance during MSL EDL is evaluated, including performance using a single 70-meter DSN antenna and an array of two 34-meter DSN antennas as a back up to the 70-meter antenna.

An Interplanetary and Interagency Network - Lander Communications at Mars

The Mars Express Lander Communications subsystem (MELACOM) was initially designed as a relay for communications with the BEAGLE-2 lander. The failure of the landing over Christmas 2003 made its attempted use with BEAGLE-2 from January to February 2004 unsuccessful. However, intrinsic to the design was the capability for cross-support with other landers via the implementation of version 2 of the draft Proximity-1 protocol, CCSDS 211.0-R-2, which was designed to ensure reliable data transfer between remote autonomous communication nodes operating in close proximity. Reliability of the

Relay support for the Mars Science Laboratory and the coming decade of Mars relay network evolution

In the past decade, an evolving network of Mars relay orbiters has provided telecommunication relay services to the Mars Exploration Rovers, Spirit and Opportunity, and to the Mars Phoenix Lander, enabling high-bandwidth, energy-efficient data transfer and greatly increasing the volume of science data that can be returned from the Martian surface, compared to conventional direct-to-Earth links. The current relay network, consisting of NASAs Odyssey and Mars Reconnaissance Orbiter and augmented by ESAs Mars Express Orbiter, stands ready to support the Mars Science Laboratory, scheduled to arrive at Mars on Aug 6, 2012, with new capabilities enabled by the Electra and Electra-Lite transceivers carried by MRO and MSL, respectively. The MAVEN orbiter, planned for launch in 2013, and the ExoMars/Trace Gas Orbiter, planned for launch in 2016, will replenish the on-orbit relay network as the current orbiter approach their end of life. Currently planned support scenarios for this future relay network include an ESA EDL Demonstrator Module deployed by the 2016 ExoMars/TGO orbiter, and the 2018 NASA/ESA Joint Rover, representing the first step in a multimission Mars Sample Return campaign.

Mars UHF relay telecom: Engineering tools and analysis

A compact set of tools have evolved for engineering analysis of Mars UHF relay telecommunications performance at NASAs Jet Propulsion Laboratory. The tools model all telecom variables from the RF layer up through the protocol link layer. The tools can solve for point solutions, analyze dynamic performance based on link geometry and can generate a variety of multi-day performance statistics. The telecom parameters and models in the tool set have been derived from or vetted against laboratory and Mars in-situ telecom performance measurements. The tool set and underlying models feed forward into mission specific flight operations software tools, proving to be invaluable for UHF telecom systems engineering analysis at all phases of mission life cycles.