Johnson, Charles L.

Lockett, Tiffany E.

Matus, Joseph A.

NASA Technical Reports Server

NASA's Near Earth Asteroid Scout Mission
Status, History, and Lesson’s Learned
Les Johnson, Tiffany Lockett, and Joe 
Matus
NASA George C. Marshall Space Flight Center
Science and Technology Office
1
https://ntrs.nasa.gov/search.jsp?R=20190028698 2019-09-26T20:13:05+00:00Z
Near Earth Asteroid Scout
GOALS
• Characterize one candidate NEA with an imager 
to address key Strategic Knowledge Gaps 
(SKGs) for Human Exploration
• Demonstrate low cost capability for NEA 
detection and reconnaissance
• (And fly a solar sail in interplanetary space!)
Measurements: NEA volume, spectral type, 
spin and orbital properties, address key 
physical and regolith mechanical SKGs
2
Target Asteroid: 1991 VG
• Diameter ~ 5 -12 meters
• Rotation period between a few 
minutes and less than 1 hour
• Unlikely to have a companion
• Unlikely to retain an 
exosphere or dust cloud
– Solar radiation pressure 
sweeps dust on timescales 
of hours or day
Near-Earth Asteroid 1991VG (marked with green lines) on 2017 May 30. This is a 
composite of 7 images obtained with the ESO VLT. These images have been combined, 
tracking the position of the asteroid. The stars appear trailed due to the motion of the 
asteroid during each series. 
Credit Hainaut/Micheli/Koschny 3
NEA Scout Launch
NEA Scout is one of 13 secondary payloads launching on SLS EM-1
4
NEA Scout Spacecraft
NEA Scout is an interplanetary spacecraft stuffed into a 6U cubesat
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6U Cubesat Form Factor: 30 x 20 x 10 cm
Avionics/Science
Boom Deployers
Spooled Sails
RCS System
3U
2U1U
“Most difficult game of Tetris ever played”
6
Camera 
(JPL)
Solar Sail / AMT 
Controller Board 
(MSFC)
Star Tracker / RW 
Driver (BCT)
Iris Radio 
(JPL)
CDH 
(JPL)
EPS 
(Sierra 
Lobo)
Interface 
Board (JPL)
Radio LNA & SSPA 
(JPL)
A fully functional planetary 
spacecraft in a shoebox
NEA Scout Flight System
7
HaWK Solar Panel
3 Strings X2 
(MMA) 2Ux3U Solar Panel 
and MGA (BCT)
2Ux3U Solar Panel 
3 Strings (BCT)
RCS 
(VACCO)
Sail (MSFC)
Solar Panel 
Restraints X4 
(MMA/TBD)
Reaction 
Wheels (4) 
(BCT)
Rx & Tx LGA 
(JPL)
GSE Connector & 
Sep. Switches 
(COTS)
(Hidden) Rx & Tx 
LGA, Sun Sensor
(JPL/BCT)
Sun Sensors 
(BCT)
Sail Deployer (MSFC)
AMT (MSFC)
IMU (Sensonor)
A fully functional planetary 
spacecraft in a shoebox
NEA Scout Flight System
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NEAS Configurations
Stowed in Dispenser
Ejection, before panel deployments
Configuration before sail deployment
Sail deployed
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~9 x ~9m Solar Sail 
6U 
Stowed 
Flight 
System
School Bus
Deployed Solar Sail
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86m2 Sail in <2U
Dispenser Tabs
86m2 Solar Sail
RCS Interface
Stainless Steel Booms
Stepper Motor Driven Deployer
Free Rotating Spool
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Full Scale Sail Assembly
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Flight Sail Testing
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NEA Scout Flight Operations
System Performance:
0.07 mm/sec2
25 g/m2
14
Before There Was NEA Scout
• 2010
– Multiple Near Earth Object 
Rendezvous Using Solar Sails
• 5000 square meter solar sail
• Sail system mass = 71 kg
• Total spacecraft mass = 340 
kg
• Estimated cost = $91M
15
Before There Was NEA Scout
• 2012
– Near Earth Object Precursor
• 871 square meter solar sail
• Sail system mass = 19 kg
• Total spacecraft mass = 43 kg
• Estimated cost = $91M
16
NEA Scout & Lunar Flashlight
• 2013
– Near Earth Asteroid Scout
• >100 square meter solar sail
• Sail system mass = ~4 kg
• 12 U spacecraft bus
• Total spacecraft mass = 30 kg
• Estimated cost = $25M
– Proposal submitted to HEOMD 
– JPL proposed the same mission 
independently
– JPL also proposed Lunar 
Flashlight – an additional solar sail 
mission
– MSFC and JPL told to merge into 
a single team
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NEAS & LF Teams Merged
• 2013
– Near Earth Asteroid Scout
• 86 square meter solar sail
• Sail system mass = <3 kg
• 6 U spacecraft bus
• Total spacecraft mass = ~24 
kg
• Estimated cost = $23M
– Same solar sail for both 
missions
– MSFC develop the solar sail
– JPL develop the spacecraft
– MSFC manage NEA Scout
– JPL manage Lunar Flashlight
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Solar Sail: Common System
• Commonality of sail design for NEA Scout and Lunar Flashlight will 
minimize development costs
– Sail sized to meet propulsive requirements for both missions
– Will additionally provide reflector for Lunar Flashlight science
– Common elements include booms, materials, packaging, 
deployment and control systems
• Will seek commercial partner to 
license the sail technology for future 
NASA and commercial missions:
– Exploration (additional NEA’s)
– Science (Planetary, Heliophysics)
– Resource Identification (commercial)
• MSFC has Space Act Agreement with 
The Planetary Society for lessons 
learned on their LightSail Project
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Solar Sail: Common System
• Commonality of sail design for NEA Scout and Lunar Flashlight will 
minimize development costs
– Sail sized to meet propulsive requirements for both missions
– Will additionally provide reflector for Lunar Flashlight science
– Common elements include booms, materials, packaging, 
deployment and control systems
• Will seek commercial partner to 
license the sail technology for future 
NASA and commercial missions:
– Exploration (additional NEA’s)
– Science (Planetary, Heliophysics)
– Resource Identification (commercial)
• MSFC has Space Act Agreement with 
The Planetary Society for lessons 
learned on their LightSail Project
20
NEAS and LF Separated
• 2015
– Lunar Flashlight spacecraft 
became too heavy for a 
solar sail to provide 
sufficient propulsion
– sail removed
– Laser and chemical 
propulsion added
21
From 4 Quadrants to Single Sail
• NanoSail-D heritage 4-quadrant design with 4 
metallic booms
• LaRC analysis showed that metallic booms would 
deform, destroying sail flatness
• Single sail developed to shade the booms 
and eliminate thermal deformation 
problems
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Ideal, Flat Solar Sails
Ideal sails are perfectly flat and have 
predictable and regular light 
reflection
NASA Image
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Real Solar Sails Are Not “Ideal”
Billowed Quadrant Diffuse Reflection
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Real Sails Have Imperfections
A deployed solar sail has misaligned CM / CP needing correction
25
Active Mass Translator (AMT)
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NEA Scout AMT
Trimmed StateNominal State
AMTCP
CM
Thrust
Disturbance Torque
KEY
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NEA Scout - Status
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Flight AMT with thermocouples attached for testing
Reaction Control Unit (RCS) Flight Unit
Avionics Box Integration Flight Solar Sail Spooled on Deployer
Questions?
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