IEEE - Aerospace and Electronic Systems - March 2020 - 20

Feature Article:

DOI. No. 10.1109/MAES.2019.2958729

Near-Earth Asteroid Scout Flight Mission
Tiffany Russell Lockett, NASA Marshall Space Flight Center
Julie Castillo-Rogez, Jet Propulsion Laboratory
Les Johnson, Joe Matus, NASA Marshall Space Flight Center
Jack Lightholder, Anne Marinan, Jet Propulsion Laboratory
Alexander Few, NASA Marshall Space Flight Center

INTRODUCTION
The Near-Earth Asteroid (NEA) Scout mission will demonstrate the capability of an extremely small and inexpensive spacecraft to perform reconnaissance of an asteroid
using a low-thrust solar sail propulsion system [1], [2].
This is an extension of the solar sail technology developed
and flown by the NASA Marshall Space Flight Center 3U
CubeSat, NanoSail-D in 2010 [3], [13]. An NEA Scout
will use an 86 m2 solar sail, deployed from a 6U CubeSatbased spacecraft, to carry a camera, cold gas system, and
full avionics suite on a slow flyby of an NEA within two
years of launch (see Figure 1). Each "U" contains about
one liter in volume so that a 6U CubeSat measures only
11 Â 24 Â 36 cm (see Figure 2).
The success criterion for the mission is the development of a capability that can close strategic knowledge
gaps (SKG) at a NEA identified as a human exploration target by the Human Exploration and Operations Mission
Directorate (HEOMD). The low-thrust propulsion enabled
by the sail will allow the CubeSat to almost match the
target's velocity, with two significant advantages. A slow
relative velocity to the target will facilitate preparations for
a close flyby at < 1 km at closest approach and a long operation time in proximity to the target. These flyby characteristics are required by stringent requirements on spatial
resolution and observations under varying illumination.
To increase resiliency against launch delay, a variety
of potential targets have been identified based upon launch

Authors' current addresses: T. R. Lockett, L. Johnson,
J. Matus, A. Few, NASA Marshall Space Flight Center,
Huntsville, AL 35812 USA, (e-mail: Tiffany.
Lockett@nasa.gov). J. Castillo-Rogez, J. Lightholder, A.
Marinan, Jet Propulsion Laboratory, Pasadena, CA
91109 USA.
Manuscript received September 20, 2019, and ready for
publication December 6, 2019.
Review handled by F. Davarian.
0885-8985/19/$26.00 ß 2019 IEEE
20

date, time of flight, and ephemeris uncertainty. This first
application of a CubeSat, as a precursor mission, will pave
the way for future reconnaissance missions.
The spacecraft architecture follows the CubeSat
design mentality and approach, and is primarily based on
the use of Commercial Off-the-Shelf (COTS) parts; high
risk, lean costs, and a dynamic schedule. Screening and
testing of the COTS components provides for a more reliable design, and material added to the bus structure provides shielding for these components. However, volume
constraints limit the ability to add redundant systems to
increase fault tolerance.
This article will provide an overview of the mission,
flight system design, and unique features needed for science and propulsion.

CONCEPT OF OPERATIONS
The NEA Scout will be placed on an Earth escape trajectory by the upper stage of NASA's space launch system
(SLS) on its first flight called Artemis 1. After SLS sends
its primary payload, NASA's Orion crew capsule, on a trajectory toward the moon, NEA Scout is one of the 13
CubeSats on the flight; each will be ejected, one at a time,
from the SLS's Orion Stage Adapter. After ejection, an
NEA Scout cold gas thrusters will be used to detumble
and stabilize the spacecraft and point toward the sun to
maximize power generation and enable two-way communication with Earth.
The cold gas thrusters will provide initial delta-V
capability to target a lunar flyby, after which the solar sail
will deploy. The NEA Scout mission will use NASA's
deep space network as the primary ground system for
communications and tracking.
For a late 2020 through early 2021 launch, the NEA
Scout's primary target is asteroid 2013 WA44. However,
due to the nature of NEAs, this specific target may not be
available for later launch dates. The flexibility provided
by the solar sail propulsion system will offer alternative

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MARCH 2020

IEEE - Aerospace and Electronic Systems - March 2020

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