9. Motivation/
Background
Overview
Flight System
Technical
Resource
Budgets
Summary
Future Work
Solar Flux
Inverse Square Law
• Earth Solar Flux: 1370 W/m^2 @ 1AU
• Mars Solar Flux: 589.1 W/m^2 @ 1.525 AU
• Power generation is
proportional to the
inverse square of the
distance to the sun
Inverse Square Law
• Drives iterative process
of solar array sizing
57% Reduction in
Solar Flux Density
5/17/2015 9
10. Motivation/
Background
Overview
Flight System
Technical
Resource
Budgets
Summary
Future Work
Power Subsystem
Subsystem Component Name Quantity
EPS
Clyde Space FLEX EPS 1
CS 30 Whr Battery 1
CS Deployable Double Sided 6U Panels 4
CS 2UFixed Solar Panels 1
Clyde Space FLEX EPS
Clyde Space 30 Whr Battery
CS Deployable Double Sided 6U Panels:
• 21 cells per face
-> 42 cells on one panel
-> 84 cells one side
• Solar Cell Efficiency: 28.3%
• Area of one solar cell: 0.00275 m2
• Total Solar Cell Area: 0.231 m2
CS 2U Body-Mounted
Solar Panels
5/17/2015 10
11. Motivation/
Background
Overview
Flight System
Technical
Resource
Budgets
Summary
Future Work
Satellite Communication Bands
UHF X-Band Ka-Band
Space
Communication
Usage
Used between
landers, rovers,
and orbiters
Current
Standard in long
range
communication
s (rovers <->
Earth)
Developing
Standard
Advantages Less prone to
atmospheric
interference
Long Range
Communication
Greater Data
Transmission
Disadvantages Smaller
Distance
coverage
Requires Line of
Sight, More
power
Development &
Testing Stages,
Large
Propagation
Losses
Common Uses Broadcast TV,
Cell Phones
Radar, Deep
Space Network
Radar, Deep
Space Network
5/17/2015 11
22. Motivation/
Background
Overview
Flight System
Technical
Resource
Budgets
Summary
Future Work
Concept Summary
• Optimized Mass/Structure to fit CSD Deployer
Requirements
– Sufficient margin for future iterations of spacecraft
development
• Performed Telecommunications Link Budget:
1) Cubesat <-> Earth: Ka-Band
2) Cubesat <-> Ground: UHF
3) Cubesat <-> Orbiter: UHF
• Optimized to meet power requirements of spacecraft
bus
– Considered body & shadow shading effects
– Analysis based on Sun-Mars-Earth Angle
5/17/2015 22
28. Motivation/
Background
Overview
Flight System
Technical
Resource
Budgets
Summary
Future Work
Future Missions to Mars: 2013 - 2023
J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D
Orbiters:
ODY
MEX
MRO
MAVEN
ExoMars TGO
Landers:
Opportunity
Curiosity
InSight
ExoMars 2016 EDM
ExoMars 2018 Lander
ExoMars 2018 Rover
Mars 2020 Rover
202320172016201520142013 20222021202020192018
...
...
...
L M
18 Nov 22 Sep
...
E
E
28 Sep
19 Oct
L
4 Mar - 26 Mar
L
7 Jan - 27 Jan
...
...
19 Oct
L
7 Jan - 27 Jan
M ...
E
15 Feb- 12 Feb
L
26 Jul - 14 Aug
E
17 Jan
L
5 May - 28 May
...
...
...
...
Cruise' Aerobraking' Primary'Science'
Phase'
Funded'Extended''
Mission'Phase'
L' M E'
Launch' MOI' EDL'
Unfunded'Extended''
Mission'NoBonal'Plan'
Legend:'
5/17/2015 28
Credit: Charles Edwards, JPL
Editor's Notes
From the picture of current & future mission through 2020, the Martian Space will need plenty communication needs with Earth and potentially other assets on/orbiting Mars
Final Consideration: Cubesats have very focused missions. Not enough space to accommodate communications. Develop infrastructure using off-the shelf components to provide lower costs while increasing performance.
694634main_Pres_Mars_Comm-Nav_Evolution-Mars_Society.pdf
Although a little outdated considering NASA is considering to propose a Mars 2022 Telecommunication’s Orbiter (replacement for MRO). The objective of our concept is to provide a cheap means of satifying NASA’s communication needs in the future for missions to Mars. With the development of a dedicated cubesat telecom constellation, we can reduce costs NASA might accure through the development of expensive multi-million dollar satellite missions while allowing for NASA to continue expanding their science interests on Mars.
Talk about costs that cubesat is cheaper than dedicated comm sat or constellation of sats
charles.d.edwards@jpl.nasa.gov
MSL -> Ground asset
MRO -> Comm Orbiter
2020 Rover -> Equitorial orbit
Fix the monopole design on everywhere
MRO orbit
Here is a CAD model of the overall cubesat with labels to selected visible subsystems (this is the overall deployed view). The major subsystems that this concept looks over are the telecommunications and power systems. In the future, more analysis will be done to look at all subsystems.
When selecting external components for Cubesat, structure and sizing limitation must be put into consideration. Nevertheless, these constraints acted as driving factors in various trade studies in selection components (in particular EPS and Telecom Subsystems).
As you can see, the Deployable/Foldable components to fit 6U limitation set by the CubeSat deployment system (CSD). Note: These CSD limitations are current limitations as NASA is currently trying to expand the CSD system to accommodate for 6U Cubesats up to 14kg.
The o refers to earth.
Using the aforementioned analysis of Solar Flux, a simple solar cell sizing was conducted in order to determine what area of solar cells were needed in order to provide power to all critical subsystems. Through the solar cell sizing, it was determined that a total solar cell area of 0.246 m^2 is required, which corresponds to a total of 90 solar cells. Nevertheless, the two CS solar panel configuration were selected to provide a total of 92 solar cells. The deployable 6U panels will have to be custom made by CS (21 cells vs 18 cell current config).
Explain how the 6U body mounted is custom made as deployable. 2 of these panels. Mainly for shading
Before diving into our telecom analysis, it is important to look into the common satellite communication band that NASA is currently/plans to use in the future on Mars. (Explain left table). The right table provides a comparison of various communication bands in terms of their frequency (Ka Band high f, UHF band lowest of the three)
The table above is representative of the current telecommunication satellite relay around Mars. As the table shows, all satellites utilize X-band as their Deep Space Link (in fact it is the standard that NASA uses on DS missions). In addition for relay, UHF transceivers are utilized (UHF is the standard that NASA uses for proximity communication.
The table above is representative of the future communication relay satellite system around Mars. As we can see from the image, these future missions will continue to utilize X-Band as their DS link. Furthermore, both satellites seem to be utilizing a standardized proximity link using a JPL-standarized Electra Transceiver.
Using the two aforementioned table for current and future satellites around Mars, it can be seen that NASA is moving towards a standardization in Proximity operations around Mars through their Electra system and continuation of utilizing X-Band as their DS link. Using these as driving factors, our proposal strives to not only meet current telecom needs, but improve on them by providing alternate cost-effective ways and test novel concepts in improving telecom performance.
Mass budget here provides a preliminary estimate of the total mass of each 6U Cubesat. The mass of each component is provided (based on technical specs sheet) and a contigency factor was added in order to account of things such as custom manufacturing costs, additional weightage due to electrical wiring, harnesses, material selection, etc. As you can see, our cubesat weights around 8 kg, which is well below the max of 12 kg set by the CSD Deployer. Duto the fact that we have not sized many of the other critical systems such as thermal and propulsion, our 52% margin allows us some flexibility in future development.
The batery DoD is for the 30 Ahr CS Battery
3.7 Ahr DoD (horiz line in purple)
In general, when power generated > power draw -> charge battery
power generated < power draw -> eclipse time behind Mars (approx 36%)
With the given DoD info from CS specs, computed approx 402 days battery lifetime. Since we will have a lower DoD this will increase the battery lifetime
Cubesat <-> Earth: Worst Case is 2% of Best Case Total Data Throughput
Cubesat <-> Surface: Worst Case is 62% of Best Case Total Data Throughput
CubeSat <-> Orbiter: Worst Case is 20% of Best Case Total Data Throughput
Mass/Structure: Optimized configuration meets CSD deployer requirements
Telecom:
Performed Link Budget to see if DTE/DFE was possible. Ka Band + KaPDA (high gain) allow for communication
UHF capability to talk with other assets (mainly Electra Radio compatible)
Power:
Optimized to meet power requirements of s/c bus (mostly dictated by telecom subsystem in operational mode)
Considered shading effects (both body and shadow) due to Ka Antenna primarily
Using ephemeris data, found max solar angle and optimized Solar Cell system based off worst case scenario
MAVEN and TGO selected because they are most likely to be in service in the 2020+ timeframe
Leverages the Aerocapture CubeSat concept for deployment of CubeSats into a near-equatorial orbit during approach
Mass/Structure: Optimized configuration meets CSD deployer requirements
Telecom:
Performed Link Budget to see if DTE/DFE was possible. Ka Band + KaPDA (high gain) allow for communication
UHF capability to talk with other assets (mainly Electra Radio compatible)
Power:
Optimized to meet power requirements of s/c bus (mostly dictated by telecom subsystem in operational mode)
Considered shading effects (both body and shadow) due to Ka Antenna primarily
Using ephemeris data, found max solar angle and optimized Solar Cell system based off worst case scenario
This is a preliminary cost budget of the components selected for developing the cubesat. A few assumptions were made in computing the total cost of cubesat constellation. First off, any specific component with a cost of $0 is not really free but components which are either currently under development and/or price of component is not currently available. Nevertheless, to compensate for this, a hefty margin of 25% was added when computing the overall total costs. In addition, another assumption made is that the cost only looks at the developing the cubesat itself and does not look into other costs such as launch, DSN costs, etc. For some components such as ISIS Monopole antenna, a larger contingency was added to account for currency conversion (here from euros to USD) as well as export or tax costs.
Assumptions in analysis:
Cubesat is inertial
Parabolic dish on right-side of front view
Orbit of cubesat lies on Martian ecliptic plane and martian orbit lies on sun ecliptic plane (i.e ignore effects of solar declination angle)
Once shading area went off the surface of cubesat (Max shading), the area of shading was set to be constant (i.e increasing angle did not effect power generated)
