PSDS3– 18 MARCH 2018

Ross (née, CAESAR)

Beau Bierhaus1, Josh Hopkins1, Ben Clark1,2, Robert Jedicke3, 

Michael Ravine4, Driss Takir5

1Lockheed Martin, 2Space Science Institute, 3University of Hawaii,

4Malin Space Science Systems, 5SETI

18 March 2018

PSDS3 Workshop
PSDS3– 18 MARCH 2018 2

CAESAR Renamed for Mary Ross

• Our mission was originally named CubeSat Asteroid Encounters for Science 

And Reconnaissance (CAESAR)

• A comet mission selected for New Frontiers Phase A is also named CAESAR

• To avoid confusion, we changed our mission name to Ross

• Mary G. Ross was an engineer at Lockheed from 1942-1973, and one of the 

first American Indians in aerospace engineering

– She worked on P-38 aerodynamics, Constellation 

aeroelasticity, Polaris hydrodynamics, the Agena

rocket, and interplanetary trajectory design to 

Mars and Venus

– We honor her trailblazing role and her contributions

to orbital mechanics with this mission

Image courtesy of Society of Women 

Engineers National Records, Walter P. 

Reuther Library
PSDS3– 18 MARCH 2018 3

Ross Mission Overview

Study objective

• Demonstrate that a fleet of small, low-cost spacecraft provides 

an affordable means to explore an incredibly diverse smallbody population via flybys

Why flybys?

• A well-planned and executed flyby on an unexplored object 

provides a wealth of information on multiple fundamental 

physical parameters

• Flybys provide an excellent balance between valuable data and 

implementation with small-scale spacecraft
PSDS3– 18 MARCH 2018 4

Numbers & Processes Matter

Small asteroids are among the most 

numerous objects in the solar system

• Most objects in the solar system 

belong to a physical scale that has 

never been visited by spacecraft

• Small (< a few km) objects are . . . 

– The vast majority of planetary bodies 

(NEOs, MBAs, KBOs)

– A window into early stages of planet 

formation

– The greatest remaining unknown risk 

for Earth impact

– Candidate targets for ISRU and / or 

human exploration
PSDS3– 18 MARCH 2018 5

Bennu

Geographos Bacchus

Ast. 153591 1998KY26

Castalia 1996HW1

1998ML14

Ra-Shalom Itokawa

2008 EV5

YORP

Golevka

Why small NEOs?
RCH 2018 6

Sun

2000 BM19

V

 within

ecom

Earth Ross 

Launch

PSDS3– 18 MA

Mission Architecture

• Multiple identical CubeSats launch as secondary payloads on the same 

launch. 

• Each CubeSat targets one flyby of a different NEO. Asteroid 2000 BM19 used 

as an example throughout this presentation.

• CubeSats reside in heliocentric orbit before encounter

– Dozens of feasible targets with low Δ

– 1 year phasing orbit keeps spacecraft

~0.7 AU of Earth, which simplifies tel

• Feasible target selection considers:

– Mission duration & ΔV

– Encounter velocity & phase angle

– Earth range at encounter

– Max Earth & Sun range in cruise

– Asteroid size, orbit determination

– Science merit of target
PSDS3– 18 MARCH 2018 7

Spacecraft Configuration

• 12U spacecraft, compatible with 

rail or tab dispensers

– 24 kg launch mass with margins

• Two science cameras 

– Malin ECAM visible 

– Malin IR3 microbolometer

• X-band telecom: IRIS v2 radio and 

high-gain + low gain patch 

antennas

• Green propellant propulsion 

system from VACCO

• Deployed, non-gimbaled solar 

arrays 

Low Gain Antenna

IR Camera

Vis Camera

Star Tracker / GNC

VACCO Propulsion High Gain Antenna

Deployed Solar Array
PSDS3– 18 MARCH 2018 8

Overall Concept of Operations

• Simple, low-activity operations during cruise prior to 

encounter

– Periodic system check-outs and status

• Observe target several hours before closest approach

– science observations (next slides)

– Refines ephemeris

• Update flyby timing based on point-source observations

• Conduct flyby observations (next slides)

• Data downlink after flyby observations end
PSDS3– 18 MARCH 2018 9

Red box is IR camera FOV

White box is VIS camera FOV
PSDS3– 18 MARCH 2018 10

Incidence angle animation

Emission angle animation

Shape Matters

We developed tools to evaluate 

irregular shapes and optimize 

science-data acquisition
PSDS3– 18 MARCH 2018 11

Encounter Performance (2000BM19)

474 pix Maximum object size in pixels in visible

2.53 m/pix Best pixel scale in visible

57 pix Maximum object size in pixels in IR

20.90 m/pix Best pixel scale in IR

For a closest-approach distance of 125 km
PSDS3– 18 MARCH 2018 12

How does this compare with 

existing asteroid data sets?
PSDS3– 18 MARCH 2018 13

Itokawa
PSDS3– 18 MARCH 2018 14

enveloping pixel dimensions 

of object: white box

height: 186 pixels

width: 97 pixels

image st_2367483953_v image st_2368423234_v

89 pixels

image st_2367939436_v

height: 167 pixels

width: 111 pixels

height: 224 pixels 

width: 111 pixels

image st_2367722441_v image st_2367541069_v

height: 154 pixels

width: 108 pixels

height: 156 pixels

width: 100 pixels
PSDS3– 18 MARCH 2018 15

Ida (and Dactyl)
PSDS3– 18 MARCH 2018 16

image h1400

enveloping pixel dimensions of object

width: 58 pixels 

height: 23 pixels 

image h6100

width: 70 pixels 

height: 41 pixels 

Dactyl

width: 87 pixels 

height: 68 pixels 

image h6100
PSDS3– 18 MARCH 2018 17

width: 220 pixels 

height: 144 pixels 

image i0600

image i2000

width: 457 pixels 

height: 348 pixels 
PSDS3– 18 MARCH 2018 18

image i2278

width: 25 pixels 

height: 33 pixels 

Dactyl

image i2439

width: 297 pixels 

height: 439 pixels 
PSDS3– 18 MARCH 2018 19

Ross Provides Data to Advance 

Planetary Science

• Ross flyby data provide the needed resolutions and coverage 

to address fundamental science objectives for size, shape, bulk 

properties, and fundamental surface processes

– Significant contribution to small-body science, and planetary formation

• Flybys naturally provide a range of phase angles, incidence 

angles, and emission angles

– High-phase angle imaging (typically approach and departure) provides 

shape and surface geomorphology

– Low-phase angle imaging (typically near closest approach) provides 

information on albedo and shape

• Other discoveries possible: satellites, and other environmental 

effects

– Dactyl was detected as a satellite when just a few pixels across
PSDS3– 18 MARCH 2018 20

Telecom 

• Returning data from a planetary 

CubeSat is slow but feasible

– Earth range is important

2000 BM19 Encounter(8000 bps)

Max Range During Mission(500 bps) 

• Data downlink strategy leverages low-overhead, initial return of 

“thumbnail” images to:

– Select highest priority images for return

– Of those images, the “windowed subset” of each image that contains the object

– Enables fully-informed decision making to return highest-priority images, and 

preserves all data for complete download in the future if contacts available
PSDS3– 18 MARCH 2018 21

Propulsion 

• Even trajectories with near-zero nominal ΔV need a non-trivial 

propulsion budget

– Correction for launch vehicle dispersions

– Trajectory modifications across the ~3 week launch period

– Statistical trajectory correction maneuvers

– Reaction wheel desaturation

• Options considered:

– cold or warm gas systems, insufficient impulse

– electric propulsion, needs larger solar arrays with gimbals, has more 

mission ops complexity

• We selected a ~2U VACCO green monopropellant integrated 

propulsion unit, which provides higher thrust and sufficient Isp
PSDS3– 18 MARCH 2018 22

Technology Development

• Receiver noise floor improvements

– Current CubeSat radios do not have sufficient performance to receive 

DSN commands through omni-directional antennas. Improved noise 

performance would support more robust contingency scenarios.

• Ka-band development

– Ka-band communications would improve data rates from sizeconstrained small spacecraft. However, CubeSat-class radios that 

support Ka-band from deep space have not yet finished development.

• Low power / high efficiency telecom 

– current low-power telecom systems tend to be least efficient
PSDS3– 18 MARCH 2018 23

Summary

• Ross explores a largely unknown class of planetary object and 

returns compelling new observations, complementary to 

larger-scale missions

• We examined a broad range of tradespace, and have found 

small-body encounters that fit within CubeSat capabilities

• Though small in scale, these are fully functional planetary 

spacecraft and missions and need systems engineering, design, 

and test strategies appropriate to deep space missions

Copyright 2018 Lockheed Martin Corporation, All Rights Reserved