01 SURVEYOR ROVER

 

 

REQUIREMENTS, CONSTRAINTS AND CHALLENGES

 

 

 

October 24, 1997

 

 

J. Matijevic

 

 

REQUIREMENTS

 
  • Mission Objective (Rover perspective):

  • Deploy a rover on the surface of Mars between 1/16/02 to 2/5/02.

  • The rover mission is to document and collect a set of samples (soil and rock). Samples collected and suited for retrieval by a sample return mission, nominally launched in ‘05.

     

  • Rover mission parameters:

  • traverse up to 100m per sol

  • have a top speed of 6cm/sec on level ground

  • traverse up to 10km (integrated) over the mission

  • last up to one earth year

  • accommodate a payload of up to 15kg

     

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  • Communication is through a relay system :

  • 01 rover to 01 orbiter, backup through 98 orbiter.

  • Daily communication with uplink of 8kbps, downlink 128kbps, limited to as many as 2, 6-10min passes per sol, approximately at 4:00 and 16:00 LST.

  • Maximum 40Mb total downlink per sol.

     

    OPERATION

     

     

  • There are 3 rover operational modes:

  • Distance Traverse. Rover leaves site and drives to new area of investigation. Periodically during the drive the rover images area in front and provides the data documenting the drive. Rover stops near site.

  • Local Operation:

  • Survey. At site rover takes large format image. Ground controllers select targets for additional investigation and types of observations to be performed at targets. These are objectives for survey of the site.

  • Sampling. After evaluation of target data, sampling determined to be feasible/desirable. Rover collects sample.

  • Battery Charging. Rover sits and charges its battery. Depending on state this may also be an engineering day (e.g., measurement of health status, emptying data buffers, etc.)

     

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    OPERATION (cont’d)

     

  • Constraints during operation:

  • Getting off the lander, calibrating in order to begin operation

  • battery is dead on arrival - need perhaps 2 recharge days

  • (at least) one communication loop to confirm rover ready to drive

  • rover image of landing site (rover has only wide field camera)

    - 1mrad/pixel, 8bits per pixel, 45deg x 360deg or 785 x 6283 array or about 40Mb image (uncompressed) or about 2 sols for image to be returned

     

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  • Distance traversed on a given sol

  • a function of payload operation:

  • how long to communicate imagery and other data prior to selecting targets for closeup investigation

  • how long to evaluate target (rock or soil) prior to collecting a sample

  • decision about obtaining/keeping a sample

     

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    • EXAMPLE OF OPERATION

     

  • As an example, (one perspective on operation)

  • survey data : site imagery alone may require 2 sols for transmission; other spectral sweeps may require an additional 1 or 2 sols to acquire and communicate

  • driving to a selected target then taking a (set of) measurements may require up to 2 sols.

  • depending on number of targets investigated at the site, perhaps 2 sols per target

  • at least 1 sol (and maybe 2) to collect and confirm acquisition of a sample before driving on.

  • in scenario below there are 7 sites, 7 targets, 1 sample :

    •
    7 sol driving to sites
    14 (=2*7) sols of site survey data acquisition/communication
    7 sols for transmitting target measurements
    2 sols for sample collection
    -------------------------
    30sols
    + 3 sols to get off lander and begin operation
    + 2 sols battery charging
    = 35sols

    ===> 5 weeks and the rover is 300m away from the lander

     

    EXAMPLE OF OPERATION

     

     

     

     

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    NEED FOR TECHNOLOGY DEVELOPMENT

     
  • Implementing the above scenario: on a given sol

  • drive with some precision 100m to a new location : improvement in hazard avoidance and navigation over "Sojourner"

  • correct position and deploy an instrument package at a target location : terminal guidance system using information available on the vehicle

  • collect a soil or rock sample

     

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  • Improving coverage and mission return:

  • define obseration requirements at a target and build these requirements into commanded action (e.g., location on rocks/soil for measurement, sun angles for imagery)

  • enhance returned data

     

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  • Maximizing use of operational days:

  • let the rover driver to a site, collecting data along the way, without an intervening command cycle [addresses issues associated with missed opportunities for downlink or delay in command receipts through the ground/orbiter system]

  • let the rover drive and collect data at a target without an intervening command cycle

     

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    NEED FOR TECHNOLOGY DEVELOPMENT (cont’d)

     

     

  • Other on-board improvements:

  • resource management on the rover : power, data, thermal, battery SOC

  • knowledge of vehicle kinematic state

  • Ground control station based tools:

  • enhanced terrain mapping

  • correlation of rover-based imagery : widefield and closeups

  • simulation of articulation of vehicle dofs

  • organization and planning of vehicle observations

  • development of command sequences to be uplinked to the rover

  • organization of remote science teams, collecting and modifying objectives

     

     

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    CONSTRAINTS

     

  • Schedule constraints:

  • rover system PDR 6/98 - identify and establish resource estimates for all rover hardware and software

  • rover system CDR 6/99 - prior to receiving ‘go ahead’ to build, identify all rover hardware and software and how they will be used to carry out the mission

  • FUR preshipment around 9/00 - final software load prior to integration with lander.

  • FUR close-out at the Cape 2/01 - Last chance to modify parameters and load program patches.

  • launch + 30 days 5/01 - identify tools for use in ground operation.

  • 12/01 (30days before landing) - show all ground operation tools in configuration ready for baseline ‘freeze’.

     

     

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    CONSTRAINTS (cont’d)

     
  • Resource constraints: (baseline)

  • rover total mass allocation less than 45kg

  • (mobile) 22kg rover, 15kg payload

  • (support) 8kg lander mounted rover equipment

  • rover power production:

  • solar panel maximum less than 16W(winter), 50W(summer). Possibly less than 100Whr/sol at certain landing sites

  • energy storage : 10A-hr

  • dust accummulation : 0.2% per sol

  • rover computer

  • Synova Mongoose-V (R3000) rad-hard 32bit CPU (base on MUSES-CN design study ~10MIPS @ 12MHz) running VxWorks operating system

  • 4-6 Mbytes RAM, 1-2 Mbytes PROM, 16-64 Kbytes EEPROM

  • ~0.5Gbit solid state recorder (SSR) or equivalent mass storage capability

  • RS-422 communication bus and analog/digital I/O

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  • rover telemetry:

  • up to 40Mb per sol, perhaps not more than 25Mb per pass

  • limited ability to prioritize and ensure transmission to earth

     

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    • ROVER CONTROL AND NAVIGATION

    (Current Baseline)

     

    Rover Computer

  • Synova Mongoose-V (R3000) rad-hard 32bit CPU (base on MUSES-CN design study ~10MIPS @ 12MHz) running VxWorks operating system

  • 4-6 Mbytes RAM, 1-2 Mbytes PROM, 16-64 Kbytes EEPROM

     

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    Navigation sensors

  • Active Pixel Sensor (APS) based cameras

  • 3 stereo camera pairs (front, rear and mast mounted)

  • Rocker-Bogie position potentiometers

  • Accelerometers for roll/pitch

  • Sun sensor (via camera) and gyro for heading

     

    Other

  • ~0.5Gbit solid state recorder (SSR) or equivalent mass storage capability

  • RS-422 communication bus

  • Analog and digital I/O

     

    STRAWMAN ELECTRONICS BLOCK DIAGRAM

     

     

     

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