Mars Telecommunications RelayCubeSat ConstellationDavid SpencerSpace System Design LaboratoryGeorgia Institute of TechnologyNovember 20, 2014

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Concept Overview

A constellation of low-cost CubeSats in Mars orbit augments telecom relay capability for landed assets Benefits include increased frequency of command (forward link)

opportunities, and increased return data volumes from landed assets A near-equatorial constellation of 2 or 3 CubeSats provide relay between

a landed asset and either MAVEN or ExoMars/Trace Gas Orbiter (TGO) No direct-to-Earth link for CubeSats MAVEN and TGO selected because they are most likely to be in service

in the 2020+ timeframe

This concept is targeted for the 2020 opportunity, supporting M2020 Leverages the Aerocapture CubeSat concept for deployment of

CubeSats into a near-equatorial orbit, deployed from M2020 during approach

Concept is also applicable for ridealong CubeSats deployed from a future Mars orbiter, following orbit insertion

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Assumptions Evaluated coverage from 2- and 3-CubeSat constellations

2-CubeSats in a constellation phased 180° apart 3-CubeSats in a constellation phased 120° apart

CubeSat orbit altitude 350 km. Orbital inclinations of 0°, 10°, and 20° examined

Landed asset latitude of 0°, 5°, 10°, 15°, 20° Results for southerly latitudes mirror those from northerly latitudes

CubeSat relay through MAVEN or TGO MAVEN orbit: 6200 x 150 km orbit altitude, 75 deg inclination TGO orbit: 400 km circular orbit altitude, 74 deg inclination

Comm links possible when line-of-site exists between assets Return data throughput limited by CubeSat-to-Orbiter link Data rates as a function of range derived from telecom link budget, 1 W power output

STK simulations each cover 30-day time periods; results averaged

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2-CubeSats: Lander OverflightsCubeSats 0° Incl., Lander 0° Lat.

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2-CubeSats: MAVEN PassesCubeSats at 0° Inclination

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2-CubeSats: TGO PassesCubeSats at 0° Inclination

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3-CubeSat Constellation Data Volume Capability

CubeSat Constell. Inclination (deg)

Surface Asset

Latitude (deg N)

CubeSat Constell. Avg # of

Passes/Sol

CubeSat Avg. Pass Duration

(min)

CubeSat Constell. Avg. Data

Volume Per Sol via

MAVEN (Mb)

CubeSat Constell. Avg. Data

Volume Per Sol via TGO

(Mb)

0 0 34.3 17.5 254.8 640.3

0 10 34.3 16.1 254.8 640.3

0 20 34.3 10.8 254.8 640.3

10 0 34.3 16.8 265.1 693.7

10 10 34.3 15.1 265.1 693.7

10 20 23.3 12.7 265.1 693.7

20 0 34.3 14.3 273.5 810.0

20 10 26.8 14.9 273.5 810.0

20 20 20.8 14.8 273.5 810.011/20/14

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Preliminary Conclusions

CubeSat constellation provides a dramatic increase in the frequency of communications opportunities with landed assets Communications opportunities via the 2- or 3-CubeSat constellation occur

approximately every hour, compared with 4-5 passes per day communicating directly to MAVEN or TGO

Frequent uplink opportunities would be a major benefit to operations teams scheduling the building and transmission of command products

Max possible data return via CubeSat constellation is comparable to data volumes that may be returned directly through either MAVEN or TGO Ex: Equatorial 3-CubeSat constellation can return > 250 Mb/sol via MAVEN,

compared with 177 Mb/sol for surface asset communicating directly to MAVEN. Caveat: Power limitations of the surface asset may restrict the number of

telecom opportunities with the constellation.

Overall, a near-equatorial CubeSat constellation provides significant flexibility and increased robustness to both forward-link and return-link communications with near-equatorial surface assets.

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Next Steps

Evaluate alternative altitudes for CubeSat constellation 500 km, 650 km Add 10 deg horizon limit for surface-to-CubeSat links

Packaging of components into CubeSat form factor Target: 6U form factor

Further develop this concept within the context of the Aerocapture CubeSat ridealong payload deployed from M2020 Evaluate aeroshell design for accommodating 6U CubeSats Evaluate CubeSat propulsion requirements for orbit

acquisition, station-keeping

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