esa standard documentemits.sso.esa.int/emits-doc/ews5055-annex.pdfone axis mechanism guaranties a...

D O C U M E N T

document title/ titre du document

ANNEXES A AND B TO STATEMENT OF WORK

RF-OPTICAL SYSTEMS TRADE-OFF STUDY FOR INTERPLANETARY TELECOMMUNICATIONS

AO/1-5055/06/NL/EK

prepared by/préparé par TEC-ETC reference/réference TEC-ETC/2006.14/PH/ph issue/édition 1 revision/révision 0 date of issue/date d’édition 10 March 2006 status/état issued Document type/type de document Technical Note Distribution/distribution

a

ESTEC Keplerlaan 1 - 2201 AZ Noordwijk - The Netherlands Tel. (31) 71 5656565 - Fax (31) 71 5656040

ews5055-annex.doc

Annexes A and B to SoW Ref. TEC-ETC/2005.110/PH/ph

issue 1 revision 0

page ii of ii

T A B L E O F C O N T E N T S

ANNEX A: MSR MISSION DESCRIPTION ....................................................................................1 1. Overall description.....................................................................................................................................1 2. Mission Phases and Trajectories ................................................................................................................2 3. Communication architecture ......................................................................................................................3 4. MSR RF TT&C System Baseline ..............................................................................................................4 5. TT&C equipment configuration.................................................................................................................6 6. Data requirements ......................................................................................................................................8 7. Vehicle configurations, communication systems and attitudes .................................................................9

7.1.Orbiter ..................................................................................................................................................9 7.2. Ground Stations.................................................................................................................................10

ANNEX B: ACRONYMS................................................................................................................11

Annexes A and B to Annexes A and B to

Ref. TEC-ETC/2005.110/PH/ph issue 1 revision 0

page 1 of 11

ANNEX A: MSR MISSION DESCRIPTION 1

1. Overall description The Aurora Mars Sample Return (MSR) studied by ESA within the timeframe 2003-2004 includes two Ariane 5 ESC-A launches in 2011 (with back-up in 2013) bringing two separate composite spacecraft to Mars (by composite it is meant here the assembly of two or more vehicles). The composite launched as first, features an Orbiter inserted in low Mars orbit and an Earth Return Capsule (ERC). The Orbiter acts as Data Relay in the communications between Mars surface and Earth and performs the rendezvous with a Mars Ascent Vehicle (part of the second launch) carrying the sample container from Mars surface. The second composite has a Carrier and a Descent Module for landing the Mars Ascent Vehicle and the platform that performs the sample collection. The entry into Mars atmosphere is from hyperbolic interplanetary trajectory. After sample collection, the sample is sealed within a container and the container is transferred to the Mars Ascent Vehicle that carries it into Mars orbit. There, the upper stage of the ascent vehicle docks to the Orbiter. The sample container is mechanically transferred inside the Orbiter to the Earth Return Capsule. After all these operations have been performed, the Orbiter returns back to Earth and after the sealing of the container has been checked, releases the Earth Return Capsule into an Earth re-entry trajectory. The Earth Return Capsule undergoes a parachute-less descent and a hard landing and it is finally recovered. In summary, the following vehicles are part of the mission architecture: 1. MAV (Mars Ascent Vehicle): The vehicle that lifts off the sample container from the Mars

surface. 2. DM (Descent Module): The vehicle that lands onto Mars carrying the MAV and any

equipment needed for the surface operations. 3. Surface platform: The part of the DM that carries the equipment needed for surface operations

including sample collection 4. Carrier: The vehicle carrying the Descent Module and the Mars Ascent Vehicle from Earth to

their entry point to Mars 5. Earth Re-entry Capsule: The vehicle that performs the Re-entry, Descent and Landing onto

the Earth surface carrying back the sample container

1 During the course of the activity, ESA might provide the Contractor with more updated data concerning the Mars-Sample Return mission resulting from the upcoming MSR Phase A2 study.



page 2 of 11

6. Orbiter: The vehicle performing the Data Relay function between the Mars surface and the

Earth Ground System. The Orbiter is also used as Return Vehicle to carry back to its entry point to Earth the Earth Re-entry Capsule.

Two main mission options are possible depending on the way the Sample Container is passed to the Orbiter in Mars orbit for return to Earth: 1. Sample Container left on the MAV upper stage in Mars orbit and rendezvous and docking

between the Orbiter and the Upper Stage 2. Sample Container released in Mars Orbit by the MAV upper stage and rendezvous and capture

of the Sample Container from the Orbiter Presently, both options are still open. They lead principally to a different design of the MAV and slight differences in the Orbiter.

2. Mission Phases and Trajectories The trajectories for the cruises to Mars and the return to Earth are described in detail in: Mars Sample Return, 2011/2013 launch window mission analysis [AD-3]. This includes ranges and Sun-Spacecraft-Earth angles. The following main mission phases are of relevance:

Phase Duration Cruise to Mars of Composite 1 24 months Cruise to Mars of Composite 2 21 months Orbiter Mars orbit insertion 3 weeks DM release and coasting to the Mars entry point 1 month DM Entry, Descent and Landing 30 min Surface Platform Surface operations and Orbiter Data relay

3 months

MAV ascent and SC (or MAV upper stage) Mars orbit insertion

30 min

Rendezvous and Docking (or Capture)

1 month

Return Cruise to Earth of Orbiter + Earth Return Capsule

12 months

Earth re-entry, descent and landing 20 min The Mars landing site is required to be in a latitude range between 30 S and 30 N. The Mars orbit selected for the Orbiter is a 650x650 km orbit while the Rendezvous takes place in a 550x550 km orbit that is the final altitude reachable by the MAV. The orbit inclination shall match the latitude of the landing site. Therefore, inclination between –30 and +30 shall be considered.



page 3 of 11

3. Communication architecture The following links compose the mission communication architecture:

1. Carrier to Earth during cruise to Mars 2. Orbiter to Earth during cruise to Mars 3. DM to Carrier during Entry, Descent and Landing onto Mars surface 4. DM to Orbiter during Entry, Descent and Landing onto Mars surface (if allowed by

geometry) 5. Orbiter to Earth when in Mars orbit 6. Orbiter to Surface Platform during surface operations 7. Surface Platform to Earth during surface operations 8. MAV to Orbiter during ascent from Mars surface 9. Sample Container (or MAV upper stage) RF beacon for Orbiter-to-Sample Container (or

MAV upper stage) Rendezvous 10. Orbiter to Earth during return cruise to Earth 11. Earth Return Capsule beacon for Earth tracking during descent and recovery

The link characteristics are described hereafter:

Link Band Data type Note Orbiter – Earth X-band Telemetry and

telecommand + data relay

During cruise and in orbit

Carrier – Earth X-band Telemetry and telecommand

During cruise (and in orbit?)

Surface Platform –Orbiter

UHF (Proximity-1) Science data Main link during surface operations

Surface Platform –Earth X-band Low data-rate back-up DM – Carrier X-band tones Monitoring of DM

during EDL Possible back up with orbiter

MAV – Orbiter UHF (Proximity-1)



page 4 of 11

4. MSR RF TT&C System Baseline The on-board RF TT&C system used in the trade-off shall be based on the architecture proposed for the MSR mission. The main elements are:

- HGA - 2 LGA’s - 2 redundant X-band TWTAs: 34 Watt RF TX power. - 2 redundant X/X Deep Space Transponders (X-DST) - 2 redundant oscillators

Functional description The X-DST is the functional interface between the spacecraft antennas and the on-board Spacecraft Management Unit (SMU). It performs:

the phase and PSK (Phase Shift Keying) demodulations of X-Band uplink signals coming from the antenna in order to send the telecommand CCSDS frame to the command decoder of the SMU.

The PSK/PM modulation (transmitter part) of the telemetry CCSDS frames coming from the telemetry encoder (Turbo encoding) of the SMU in order to pre-amplify and transfer the X-band downlink modulated signal to the TWTA.

The ranging function (phase demodulation in receiver part) and phase modulation (in transmitter part) of the ranging signal coming from ground . The X-DST is compatible with both ESA and NASA two-ways ranging standard and the delta Dor one-way ranging. For delta Dor, ranging tones are generated by X-DST and do not require any uplink signal.

The Doppler function, using the coherent mode. The X-DST are interfaced with 2 redundant Oven Controlled Crystal Oscillators (OCXO)2. The OCXOs allow to perform ∆DOR (Delta Differential One-way Ranging) measurements during approach phase. They will ensure high stability and phase noise performances of the downlink signal. The TWTA RF output power has been optimized to 34W in order to provide the required telecommunication link, while taking into account power consumption constraints. Two TWTA’s are used in cold redundancy. The switch matrix, 3dB hybrid couplers, and diplexer provide for the TT&C subsystem the capability to drive properly the receive or transmit signal from the antenna in-use to respectively both receivers or the active TWTA/X-DST chain. It shall be outlined that the receive chains are in hot redundancy, to ensure the robustness of the telecommunication chain. Moreover, an emphasis has been placed on the absence of any single point failure even for switches. Block diagram The baseline X-Band TT&C subsystem architecture and configuration overview are shown below.

2 The OCXO might be integrated inside the X-DST



page 5 of 11

It is built around the use of the X Band Deep Space Transponder (X-DST), the 2 antenna concepts and a 34W TWTA power amplification stage. The TWTA has been sized to guaranty a least 34W RF output power, taking account power consumption constraints. The typical consumption of the TWA is of 57 W. Three X-band antennas are accommodated on the Orbiter to fulfil the transmission requirements:

one steerable X-Band High Gain Antenna (HGA), based on a dual band centre fed reflector concept. The HGA is located on –Y face of mission stage. The HGA is used as steerable around Z axis with a (+16°/-120°) rotation capability but a FOV restriction of (+16°/-80°) due to the presence of the first stage during Earth to Mars cruise phase. To insure communication around Mars the need is +30°/-90°, hence +16°/-120° FOV achieved after first stage jettisoning will give flexibility for communication during rendezvous. The HGA one axis mechanism guaranties a pointing accuracy over +/-0.5° whilst the HGA itself offers a Tx gain of 36.55 dBi and a Rx gain of 35.7 dBi.

two X-band Low Gain Antennae (LGA), based on dual frequency corrugated horn antenna

concept, one implemented on - Y face (LGA-Y) and the other one on +X (LGA+X) face of mission stage. The antenna guarantees a Tx gain of 7.8 dBi and a Rx gain of 7.6 dBi within +/- 20°. The variation of LGA gain during the mission due to Earth aspect variation versus Orbiter-Earth distance allows the TM/TC link. LGA-Y free field of view is – 60°/+ 105° with a little mask due to the HGA feed horn.



page 6 of 11

Mass and power budget

Object Units Total mass with margin [kg] HGA 1 4.40 LGA 2 0.22 TWT EPC 2 2.10 TWT 2 1.60 X-DST 2 6.60 Oscillator 2 0.22 Waveguides + RF misc. 1 1.48 Total 16.70

Object Power consumption – no comm [W]

Power consumption - comm [W]

X-DST 24 24 TWTA+EPC 0 110 APM 0 11 Total 24 145

5. TT&C equipment configuration

For the HGA antenna accommodation, a lateral face of the Orbiter is preferred as this face is remaining free. By convention this face is called the –Y face. The antenna hold down and release mechanisms will be released to allow a + 16°/- 80° rotation with the propulsion stage and a + 16°/- 120° rotation without so especially during the Terminal Rendezvous for RF coverage. This tracking range imposes a driving mechanism to be located at the base of the antenna. A rotary joint is also needed merged with the previous mechanism. The LGA antennas are accommodated one on the same face as the HGA, the other one at the opposite panel (+Y) of the Orbiter. This allows a transposition between the HGA and the –Y oriented LGA antennae during reconfiguration phases. During all the mission phases, the LGA necessary coverage is compatible with the HGA position. The lines of sight and the fields of view of the X-band equipment are given in the following table and are illustrated in the figure below.



page 7 of 11

The UHF Relay Antenna is accommodated along the +Y panel. The line of sight (+Y) and the fields of view (± 90°) of the UHF-band equipment are illustrated on figure below.



page 8 of 11

6. Data requirements

The data rate requirements depend on the actual mission scenario. Indeed, two mission options are currently still open: one in which the surface asset that collects the Mars sample is not mobile and another one in which a Rover is used. The second option is more demanding in terms of data-return. Note that the requirements correspond to the science data that needs to be transmitted from Mars surface to the Orbiter.

Option 1: Fixed surface asset In addition to the vehicle housekeeping, the following science data needs to be transmitted data from Mars surface:

1 Gbit total compressed data from panchromatic camera (over mission) 1 Gbit total compressed data from Ground penetrating Radar (over mission) 1 Mbyte per sol3 data from drill system

Option 2: Mobile surface asset (Rover)

Based on the requirements from ExoMars, 250 Mbit/sol needs to be transmitted from Mars surface (to the Orbiter). 3 A sol is one Martian Day or 24.66 hours



page 9 of 11

Besides, we have the following requirements during other mission phases:

Data transmission during rendezvous: 364 Mbits/day Data transmission for MAV launch: 1.3 Gbit in 3 days.

7. Vehicle configurations, communication systems and attitudes

7.1.ORBITER

The Orbiter is composed of the Orbiter proper and a Propulsion Stage that is used for all the manoeuvres until Mars orbit insertion and it is later jettisoned. The Orbiter proper is box-like with deployable Solar Arrays.

The +X side hosts the Rendezvous and docking/capture mechanism The –X side hosts the interface to the propulsion stage The –Y side hosts the steerable HGA The +Y and +X sides host the ERC

Earth Return

Orbiter

Propulsion Stage (jettisoned after Mars orbit insertion)



page 10 of 11

7.2. GROUND STATIONS

The Perth New Norcia and Cebreros Ground Stations have been assumed as baseline for the MSR mission with at least 6.5 hours visibility window per day, except during superior solar conjunction.



page 11 of 11

ANNEX B: ACRONYMS APM Antenna Pointing Mechanisms CCSDS Consultative Committee for Space Data Systems ∆DOR Delta Differential One-way Ranging DOR Differential One-way Ranging DM Descent Module EDL Entry, Descent and Landing EPC Electric Power Conditioner ERC Earth Re-entry Capsule ESA European Space Agency ESC Etage Supérieur Cryotechnique ESTEC European Space Research and Technology Centre FOV Field-of-view G/S Ground Station HGA High Gain Antenna LGA Low Gain Antenna MAV Mars Ascent Vehicle MGA Medium Gain Antenna MSR Mars Sample Return NASA National Aeronautics and Space Administration OCXO Oven Controlled Cristal Oscillator RF Radio Frequency PSK Phase Shift Keying PSK/PM Phase Shift Keying/Phase Modulation SMU Spacecraft Management Unit TBC To Be Confirmed TC Telecommand TN Technical Note TM Telemetry TT&C Tracking, Telemetry and Command TX Transmit TWT Travelling Wave Tube TWTA Travelling Wave Tube Amplifier UHF Ultra High Frequency X-DST X-band Deep Space Transponder

esa standard documentemits.sso.esa.int/emits-doc/ews5055-annex.pdfone axis mechanism guaranties a...

Documents