Hayabusa Asteroid Surface Sample Return

A Joint Japanese/U.S. Mission

September 2009

Don Yeomans (JPL)

U.S. Project Scientist

Asteroid (25143) Itokawa

~ 535 x 294 x 209 m (principal axes)

Retrograde rotation period = 12.1 hours about shortest

axis. Pole nearly perpendicular to ecliptic plane.

Best meteorite analog: L or LL ordinary chondrite

Albedo: 0.25 – 0.30

Bulk density ~ 1.90 +/- 0.13 g/cm3

MathildeGaspra

Ida

Itokawa is by far the smallest asteroid observed with

high resolution (i.e., smaller than Dactyl….)

Eros

(25143) Itokawa

(433) Eros

AMICA Science Camera (Jun Saito – PI) – D. Tholen, P. Smith (U.S. Co-Is)

Focal length = 12 cm, 1000 x 1024 CCD

FOV = 5.7 x 5.7 deg., 20”/px, resolution ~ 1 m @ 10 km

Filters: 7 (2 bands overlap with NIRS)

Map surface morphology to 1 m resolution

Determine spin state, colors, size, shape, volume

Search for satellites and dust ring

NIRS (Masanao Abe – PI) – F. Vilas, B. Clark

λ 0.85 – 2.1µ, Δλ = 0.0236 µ

FOV = 0.1 x 0.1 deg.,

Map mineralogical composition at 10 m scales

Characterize surface heterogeneity

Help provide link between asteroid and meteorites (with AMICA & XRS)

Search for water, space weathering

LIDAR (Tadashi Mukai – PI) A. Cheng

λ = 1.064 µ, pulse width = 14 ns, Energy = 10 mJ, cycle time = 1 s

Range = 50 m -> 50 km, accuracy = 1 m @ 50 m

Footprint = 12 x 5 m @ Home Position (7 km)

Provide accurate shape and mass determination (~10%)

Map some surface areas to maximum resolution of 1 m

XRS (Manabu Kato – PI)

Energy range: 0.7 – 10 Kev, resol. = 100 ev @1.5 Kev

Solar X-ray monitor

FOV = 3.5 x 3.5 deg.

Identify major elements (Fe, Si, Mg, Ca, Al, Na)

Identify likely meteorite analog.

Hayabusa Sampling Horn

Mission Stages (2005-2006)

Sep. 12: Arrival at Itokawa

Nov. 12: Minerva lander released (to space…)

Nov. 20 1st descent and landing. S/C on surface for ~30 minutes

(no indication that sampling pellet fired)

Nov. 26 2nd descent (no verification that sampling pellet fired)

Dec. 08 Radio contact lost – possibly due to sudden leak of attitude gas causing

S/C to spin. Attitude control lost. Earlier loss of 2 (of 3) reaction wheels.

Jan. 23 Communication re-established. Cold gas jets from canted neutralizers,

radiation pressure and the single reaction wheel used to restore attitude

control.

Apr. 25 Return to Earth initiated

2010 June 13: both sample capsule and mother S/C enter Earth’s atmosphere.

Capsule parachutes down near Woomera, Australia. Capsule recovery

aided by radar skin tracking, radio beacon and optical tracking.

Asteroid (25143) Itokawa

Sea Otter?

Black Boulders on Itokawa

Several large black

boulders have been

imaged on the surface of

Itokawa.

Largest of these is

located on the “Head” of

Itokawa.

Possible material from

another object or due to

shock blackening effects.

Touch Down Site Candidate A: Muses Sea

The largest

smooth terrain

located between

the “Head” and

“Body” of the

Otter.

~60 m across

at its widest

point.

5m

Touch Down Site Approach

(Solar angle ~10 degrees)

Touch Down Site Close-Up

Spatial Resolution: 6~8 mm/pixel (cf. NEAR: 12 mm/pixel)

Smooth Terrains on S-type Asteroids:

Eros Pond and Muses Sea

In the Middle of Muses Sea

(During the TD1 descent)

Pavement

behind JSC

Bldg.31

Relative Scale on Itokawa

Hayabusa Instrument Results

AMICA

~1500 total images taken

Entire surface mapped to 70 cm/px resolution

Highest resolution ~ 6 mm/px at landing area

Sharp edges between rough (80%) and smooth (20%) regions

Surface pebbles larger than those on Eros

NIRS

Highest resolution: 6 m @ 3.5 km altitude

Olivine rich surface: Olivine/pyroxene -> LL5-6 ordinary chondrite

Lidar

4,107,104 shots (40% hit rate)

Range: 50 m – 50 km

0.3 – 06 m regolith over surface

XRS

Mg, Al, Si obvious – ratios consistent with ordinary chondrite

composition

Summary of Science Results (Remote observations)

Size: 535 x 294 x 209 m (± 1 m, principal axes)

Rotation period: 12.1 hours, pole latitude ~ -90 deg.

Spectral similarities to LL Chondrites or Primitive Achondrites (Olivine rich)

There are slight color differences across surface – but they are within error

limits.

Very few obvious impact craters – relatively young surface

Very rough angular blocks on most of surface – rubble pile?

Largest boulder (Yoshinodai, 50 x 30 x 20 m) is ~ 10% size of asteroid

Some smooth areas seem to follow gravity wells – redder than surroundings

No extensive linear features (as there were on Eros) –> may imply no pervasive

fabric

Some high pinnacles and many boulders that seem to be just barely attached to

surface. Could be “bedrock” showing through those areas without regolith.

Surface suggestive of disruption followed by re-agglomeration – possible contact

binary

Geometric albedo: 25 – 30% (D. Tholen)

Bulk density: 1.90 ± 0.13 g/cm3

Porosity ~ 40% (similar to unconsolidated sand) assuming a chondritic

meteorite analog with a bulk density of 3.2 g/cc

Average slope range: 0 to 69 degrees; Ave. ~ 13 degrees

Escape speeds (including rotation): 0 – 19 cm/s

Back-Up Material

MINERVA – MIcro/Nano Experimental Robot Vehicle for Asteroid

12.0 x 10.0 cm, 591 g

9600 bps link to Hayabusa s/c. Maximum communication range ~ 20 km

Lifetime = 3 asteroid days (36 hours)

3 cameras (320 x 240 px); adjustable shutter speed; f.l. = 15 cm (2) & inf. (1)

Resolution < 1 mm on surface; stereo possible

6 photodiodes to detect sun direction; 4 thermal probes for surface temperature

MINERVA released ~17m from surface

Photodiodes use to orient s/c

Turntable orients s/c for next hop (~10m)

Reaction wheel causes s/c to counter rotate

and hop. Post-hop position prediction is

loose at best.

Touch Down Site Candidate B: Little Woomera

This area was

selected as one

possible landing

site.

Subsequent

high resolution

images showed

that this area still

held too many

meter-sized

boulders.

Asteroid 25143 (1998 SF36)

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

0.65 0.90 1.15 1.40 1.65 1.90 2.15 2.40 2.65

Wavelength (mm)

No

rma

lize

d R

efl

ec

tan

ce

12 March 2001 UTC

24 March 2001 UTC

Absorptions by pyroxene and

olivine are observed. Local

differences in reflectance and

wavelength –dependence are

observed.

This seems to show slight

differences in surface materials,

particle sizes, and space

weathering. Detailed analysis

is underway.

NIRS Reflectance Spectrum

~100 meters

(ISS at 15A Stage)

540 meters

Asteroid Itokawa, ISS, and Orion CEV

JAXA, NASA

Orion CEV

~17 m

(cross section)

Yoshinodai