Hayabusa Musesc and Minerva

Hayabusa (called MUSES-C prior to launch) is a Japanese near-Earth asteroid sample-return mission that includes a small mobile surface element. It carries a horn-shaped sampling mechanism that, after contact with the surface, fires small projectiles to collect the ejecta for return to Earth in a re-entry capsule. The MINERVA hopping rover - at 591 g the lightest ever planetary vehicle - was due to be deployed during descent to the surface. Hayabusa had also been due to carry a Small Science Vehicle (SSV) or 'MUSES-CN' wheeled Nanorover from JPL (PI: Yeomans) (Jones, 2000). It was, however, cancelled in November 2000 for mass and budgetary reasons. It would have carried the following payload: multiband camera (Smith), near-IR point reflectance spectrometer (Clark), AXS alpha-X-ray spectrometer (Economou), and a laser ranging system. Figure 20.4 shows MINERVA and its accommodation on Hayabusa.

Target Objectives

Prime Contractor Launch site, vehicle Launch date Arrival date

Landing site co-ordinates

End(s) of mission(s)


Payload experiments

25143 Itokawa (1998 SF36) (previously 4660 Nereus then 10302 (1989ML)) Technology demonstration (electric propulsion autonomous navigation microgravity, sampling, direct atmospheric re-entry), in situ asteroid science ISAS/JAXA + NTS Kagoshima, M-V-5 09/05/2003

Having arrived at Itokawa on 12/09/2005 for remote sensing operations, MINERVA separated from Hayabusa on 12/11/2005; Hayabusa released a target marker and contacted the surface three times and stayed 30 minutes on 19/11/2005 and once on 25/11/2005 MINERVA is believed not to have encountered the asteroid surface, due to deployment at a time when Hayabusa was moving away

Contact with MINERVA ended shortly after deployment, yet MINERVA had already successfully imaged Hayabusa and measured heat radiated by the asteroid surface. Hayabusa mission still under way at time of writing Hayabusa: launch wet mass 530 kg, incl. 50 kg chemical propellant and 65 kg of xenon

MINERVA: 591 g, plus — 0.6 kg of support equipment on Hayabusa Hayabusa:

• AMICA asteroid multiband imaging camera (ONC-T (telescopic camera) + 8-colour filters & polarisers) (Saito)

• NIRS near-IR spectrometer (Abe)

Delivery architecture Thermal aspects

Power aspects

Communications architecture EDL architecture

Landing speed(s) Active operations (deployments, etc.)

Key references

• XRS X-ray spectrometer (Okada, Kato)

• Three target markers

• Surface sampling device (Yano)

MINERVA hopper (Yoshimitsu):

• Three colour CCD cameras (one plus stereo pair)

• Thermal sensors

• Mechanical sensors

Separation of MINERVA from Hayabusa during low altitude manoeuvre and free fall to surface

MINERVA: passive control, plus sleep mode if too hot or cold, and hopping to avoid extremes

MINERVA powered by battery and Si solar array (max 2.2 W at 1 AU) with two 2.3 V, 50 F condensers

Hayabusa 2-way DTE; MINERVA two-way relay via orbiter at 9600 bits s"1

Intended method for Hayabusa: descent at 12 cm s"1 and release of target marker at — 40 m; braking to 3 cm s"1 then free fall from rest at 17 m MINERVA: separation from Hayabusa at a few tens of m altitude (at low speed) and passive free fall —0.1 m s"1

MINERVA: hopping mechanism (turntable, rotor, brake) Hayabusa: deployment of solar arrays, MINERVA, target markers, sampling mechanism and sample return capsule

Yano et al., 2002; Kawaguchi et al., 2003; Yoshimitsu et al., 2001, 2003; Science 312 (5778), 2006

Figure 20.4 MINERVA on Hayabusa.

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