NASA Mars Exploration Mission Operations Concepts Greg Kazz Chad Edwards NASA/JPL.

NASA Mars Exploration Mission Operations Concepts

Greg Kazz

Chad Edwards

NASA/JPL

18 Jan 2007Mars BoF - CCSDS Jan 2007 Meeting - Colorado SpringsCde/gjk-2

MER (Spirit and Opportunity)

• Telecom configuration– X-band: 15 W SSPA;

LGA, 28 cm steered HGA– UHF: CE-505 txcvr;

monopole antenna

• EDL– X-band MFSK tones to DSN

(~1 bps effective info rate)– 8 kbps UHF simplex – link to MGS after

backshell separation

• Surface ops– Low-latitude landing sites - Spirit (15˚S, 175˚E), Opportunity (2˚S, 354˚E)– X-band DFE commanding each Martian morning– Afternoon telemetry return via X-band DTE and/or UHF relay via ODY (reliable) or

MGS (unreliable) to support next sol(s) planning• At this point, nearly all data return is via ODY relay

– Additional telemetry return via overnight ODY/MGS relay passes as allowed by rover energy budget

– Typical 100-200 Mb/sol data return via 1-2 UHF relay passes• Most passes @ 128 kbps; some ODY passes supportable at 256 kbps

– Prox-1 User-defined data mode (bitstream structured as DTE TM frames)


Mars Reconnaissance Orbiter

• MRO represents the latest instance of a core Mars Exploration Program strategic science orbiter, equipped with relay capability– Long lifetime (6 yrs nominal; consumables for 10 yrs)– First flight of Electra UHF transceiver, Software-Defined Radio with in-

flight reprogrammability– Low-altitude polar orbit for science, 3 PM/3 AM orbit plane

• End-to-end protocol suite– CCSDS Prox-1 protocol on prox link

• Reliable and unreliable modes supported• Currently only user-defined data mode supported• Post-launch upgrade to implement Adaptive Data Rate functionality is

planned for support of MSL

– Deep space link• AOS link layer• Unacknowledged CFDP provides pass-level accountability information

– Relay operations• Nadir attitude, or roll steering (up to +- 30 deg) for enhanced relay

performance


Phoenix (PHX)

• Telecom configuration– UHF-only after cruise stage separation– CE-505 UHF txcvr, helix and

monopole antennas

• EDL– 8, 32 kbps UHF simplex link to MGS

(open loop carrier detect, closed loop demod), MRO (open loop demod), MEX (open loop carrier detect)

• Surface ops– High-latitude site (65˚ - 72˚N) offers many contact opportunities from polar

relay orbiters (ODY and MRO)– 90 sol surface lifetime– Requirements:

• 60 Mb/sol telemetry return in 2 passes (>30 Mb in afternoon LMST pass for overnight planning of next sol);

• 1 Mb/sol command load each morning (LMST)

– Prox link configuration: reliable link, 8k uncoded forward/128k coded return; user-defined data mode (bitstream structured as DTE TM frames)


Mars Science Laboratory (MSL)

• Telecom configuration– X-band: 100 W TWTA (cruise/EDL),

15 W SSPA (surface); LGA, MER-class steered HGA

– UHF: Electra-Lite txcvr; quadrifilar helix antenna

• EDL– X-band DTE MFSK tones from cruise stage sep thru landing or occultation

(~1 bps effective info rate)– High rate (≥ 2 kbps) UHF simplex link to MRO

• Surface ops– Landing site TBD (± 45˚ latitude range)– 1 Mars Year design surface ops lifetime– Nominal ops concept:

• X-band DFE command pass each Martian morning (225 kb/sol)• 3 PM MRO UHF relay pass for return critical telemetry to support planning for

next sol; additional MRO relay return at 3 AM MRO pass• 250 Mb/sol aggregate data return requirement• Prox link configuration (MRO primary): reliable link, Adaptive Data Rate, 1 - 1024

kbps, user-defined data mode (bitstream structured as DTE TM frames)


2nd Decade Missions

• 2011 Mars Scout– NASA has selected two aeronomy science orbiters for further

study; downselect in late ‘07– Per AO, selected mission will carry single-string Electra payload

and serve as additional Mars relay asset after completion of orbiter’s primary science mission

• 2013 Mars Science Orbiter (MSO)– Long-lived core strategic science orbiter w/ relay capability

• 10-yr design lifetime; redundant Electra relay payload• Orbit driven by science objectives (at least for primary science phase)

– Science TBD based on ‘07 Science Definition Team

• 2016/2018 Mission Candidates– Astrobiology Field Laboratory

• Baseline ops concept based on MSL

– Network Landers• Four or more small static landers (a la previous Netlander concept)


Current Proximity Link Baseline (MRO)Forward Link

Forward link

• Send a file(s) containing the stream of bits to be received by the lander to MRO

- MRO can store & forward up to 10 files

• MRO uses Prox-1 reliable bit-stream to delivery file contents


Current Prox Link Baseline (MRO)Return Link

Return Link

• Accept stream of bits from lander using Prox-1 reliable bit-stream

– Encapsulates the received data into a series of CFDP PDUs which are stored on-board.

– The data are reliably transferred to JPL for file processing

– At JPL, the CFDP PDUs are processed into the file of received bits from the lander for the identified pass. This file is transferred to the User’s POCC.


Proposed Electra Prox-1 Upgrades

1. Provide Packet Service – Transmit/Receive Packets (Enables messaging)– Anticipate Need for Interoperability with ESA ExoMars Rovers– Packet Service requires variable length frames (to encapsulate packets)

• Requires modification to Electra Transmitter; Receiver handles now

2. If Packet Service is added, multiple Port-IDs required– CCSDS already defines Well-defined Port-IDs:

• 0 = Bit Stream• 1 = H/W Commands (FWD Link Only)• 2 = Packets• 3 ..7 = Currently Unassigned

3. Segment/Re-assemble Packets – Helps Electra control frame size (to balance Forward and Return Frame rates)

• Useful to handle unbalanced link conditions– Allows users to send packets > 2043 bytes

NOTE: No NASA missions have expressed requirements for changes.


Future Comm capabilities enabled by CFDP and Prox-1

• Prox-1 Message Transfer– Designate a port ID for transferring status/control messages

between vehicle controllers over proximity link (data for consumption around Mars)

– Requires Packet Service on both ends of the I/F– Requires implementation of Multiple port IDs

• Some ports consumed in local Mars Environment• Data over other ports for consumption on Earth

• Individual File transfer and data management– Current baseline (MRO) is pass file transfer using unacknowledged

CFDP/transfer frame retransmission– Data collected by MRO is collected and managed as one pass file– Mars Enterprise defined CFDP metadata and orbiter data manager

enables • Individual file prioritization• Increased file accountability (including the orbiter)• Increased ability to manage E2E data latency


Some Key Issues

– Electra baseline is a bit stream, but ESA requires packet interface.

– If packet service is used, do we need global APID management scheme or rely upon other mechanisms such as CFDP – one CFDP APID and use CFDP file names?

– Use of defined international hailing frequency for hailing. What about working channel assignments? What kind of frequency use therefore bandwidth does Exomars plan on?

– Need for future Modulations? Coding?– NASA/ESA Compatibility with the existing Prox-1 std?– End to End accountability and traceability – on frame,

packet, product basis– Use of CFDP ?– Security ?– What needs to be put in place in order to exchange

command and telemetry data operationally for ESA/NASA missions – going beyond the MER/MEX demos?

NASA Mars Exploration Mission Operations Concepts Greg Kazz Chad Edwards NASA/JPL.

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