OSIRIS- REx : Engineering Challenges of Sampling an Asteroid

OSIRIS-REX ENGINEERING CHALLENGES AT FESWG ON 1/7/14

OSIRIS-REX: ENGINEERING CHALLENGES OF SAMPLING AN ASTEROID

DAVID EVERETTJANUARY 7, 2014

PRESENTED TO THE FUTURE EXPLORATION SCIENCE WORKING GROUP AT GSFC


ABSTRACT

The Origins, Spectral Interpretation, Resource Identification, Security--Regolith Explorer (OSIRIS-REx) mission will return a sample from the Earth-crossing, carbon-rich asteroid known as Bennu. This presentation will discuss the project development as the team approaches CDR, with emphasis on some of the major engineering challenges of the mission. Although Bennu has been extensively observed from Earth (using Arecibo, Herschel, HST, Magellan 6.5-m, SOAR 4-m, Spitzer, TNG 3.6-m, VATT 1.8-m, VLT 8.4-m, WHT 4.2-m and Kuiper 1.5-m), many details critical to sampling cannot be known until OSIRIS-REx arrives at the asteroid in 2018. Scientists and engineers have worked together during the design of the mission to define the expected near-Bennu environment, bound the driving environmental requirements, and establish an operations strategy which uses knowledge gained during early observations to direct later operations. The inherent uncertainty of this mission combined with the schedule-limited nature of a planetary mission and the cost-capped approach of the New Frontiers Program make OSIRIS-REx a very interesting engineering project.

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OSIRIS-REX: RETURNING A SAMPLE FROM AN ASTEROID!

• Origins: Taking a look at carbon-rich material left over from the formation of the solar system

• Spectral Interpretation: Understanding up close what we see through telescopes from a distance, using different wavelengths

• Resource Identification: Learning about the composition and learning how to operate around an asteroid will help us utilize asteroids in the future

• Security: Bennu has a 1:2500 chance of hitting the Earth in the late 22nd Century (about 170 years from now)

• Regolith Explorer: Looking at the details of the loose material on the surface of Bennu

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OSIRIS-REX ENGINEERING CHALLENGES AT FESWG ON 1/7/14 4

WHERE HAVE WE BEEN?

Rosetta at LutetiaDawn at Vesta

Hayabusa at ItokawaNEAR-Shoemaker at Eros and Mathilda

Galileo at Gaspra and at Ida and Dactyl


WHY RETURN A SAMPLE?

• Pristine (minimal influence from Earth contact)• Known geologic context• More than what on-board instruments can tell us• Generations of study in the lab

• New researchers• New techniques


WHERE ARE WE GOING AND WHAT WILL WE GET?

ASTEROID FAST FACTS

• Sample return mission to (101955) Bennu• Pristine carbonaceous material• At least 60 grams (2.11 ounces) of material

(and as much as 2 kilograms or 4.4 pounds) • A time capsule from the early Solar System!

• Near-Earth asteroid• About 500 m (⅓ mile) diameter• 4.3-hour rotation period• 436.6-day orbit of Sun• Ancient carbon, volatiles• Rocky fragments with fractures and pores

(~1 g/cc bulk density)• Potential hazard to Earth

Actual Radar Image

Simulated Image


MISSION TIMELINE

• Launch in September 2016• Earth flyby in September 2017• Arrive at Bennu in October 2018• Map the asteroid and select a sample site• Sample in Summer or Fall 2019• Depart in March 2021• Arrive at Earth September 24, 2023

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FLIGHT SYSTEM FACTS

• 1955 kg (4310 lbs), half is fuel!• 2 meters (6.6 feet) per side• 1200 W• 8.5 m2 (91 square feet) of solar

panels • Lithium ion batteries• 5 Instruments:

• Measurements in x-ray, visible and infrared

• Laser measurements• Touch-and-Go Sampler• Sample Return Capsule

It’s based on other planetary missions (MAVEN, Juno, MRO)


TOUCH AND GO SAMPLE ACQUISITION MECHANISM

Elbow

Shoulder

Wrist

Hand (Sampler Head)


NADIR DECK


EXPLORATION OF THE UNKNOWN

• OSIRIS-REx must retrieve sample from an asteroid that has never been seen up close

• Design Reference Mission provides the step-by-step plan to build our knowledge• Created and maintained by project systems engineering team• Touches all aspects of the mission design• Drives mission architecture and requirements

• Design Reference Asteroid documents what we do know about Bennu and how well we know it (uncertainties)• Created and maintained by the science team• Based on many observations (Arecibo, Herschel, HST, Magellan 6.5-m,

SOAR 4-m, Spitzer, TNG 3.6-m, VATT 1.8-m, VLT 8.4-m, WHT 4.2-m and Kuiper 1.5-m) as well as analysis

• Peer-reviewed information• Drives some aspects of environmental requirements document

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• The DRM is the mission-level (L2) operations concept for OSIRIS-REx• Provides an end-to-end, detailed description for how the mission

addresses the OSIRIS-REx science objectives and engineering drivers• Includes 13 mission phases, from launch through Bennu proximity

operations, to delivery of the sample to the curation facility following Earth return

• Defines technical criteria for transitioning from one mission phase to the next, including both science and navigation criteria

• OSIRIS-REx DRM themes• Focus on the sample: context, collection, & safe return• Exercise a slow, methodical, deliberate approach• Apply lessons learned• Reduce operations risk and increase sample context knowledge with

each step

What is theDesign Reference Mission?


MISSION TIMELINE


Terminator Orbit Plane

(Edge On)De-

Orbit Burn

Checkpoint Burn

Matchpoint Burn

Slew to Inertially Fixed

Attitude

Lidar Range Threshold Crossing

Lidar Range CheckTo Sun

Rotation Directio

n

To Earth

Timeline3.6 hr 18 min 2

min 10 min 8 minDe-Orbit

BurnLidar Range

Threshold CrossingLidar

Range Check

Checkpoint Burn

Matchpoint Burn

TAG

TAG

TAG OPERATIONS CONCEPTMSDD-1


GUIDED TAG APPROACH

• Orbit knowledge error and orbit departure maneuver execution error lead to large dispersion at Checkpoint

• Range threshold and pre-Checkpoint LIDAR measurements allow closed loop corrections to Checkpoint maneuver to achieve original Matchpoint location

• Matchpoint corrected to original TAG approach trajectory

Without guidance With guidance


DESIGN REFERENCE ASTEROID• Orbital Properties

• Known extremely well, through ground-based astrometry and radar observations in 1999, 2005, and 2011

• Approach imagery will be easy• Bulk Properties

• Size and shape known to within about 10 m• Mass and density uncertainty is reasonable for navigation analysis

• Rotational Properties• Spin rate known to 0.05%• Pole known to within 2 degrees

• Radar Properties• Does not drive mission design

• Photometric Properties• Drives camera design

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DESIGN REFERENCE ASTEROID (CONT.)

• Spectroscopic Properties• Drives spectrometers

• Thermal Properties• Thermal model used for spacecraft thermal analysis • Thermal modeling done with engineering feedback to ensure

results were useful • Engineering tools assume spherical object

• Surface Analog Properties• Used for TAG simulations

• Environmental Properties• Satellites (stability, size limit, etc.)• Dust

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SUMMARY

• OSIRIS-REx will return a sample from asteroid Bennu• Launch in September 2016• Rendezvous in October 2018, spend a year selecting site• Sample in mid-2019• Depart in March 2021• Return September 24, 2023

• Challenging proximity operations, especially the touch and go (TAG)

• Excellent collaboration between science and engineering team members• Using the best information available to design the mission• Engineers understand the limitations of the science knowledge—

adding robustness (margin) to compensate for the unknown

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OSIRIS- REx : Engineering Challenges of Sampling an Asteroid