JAXA Space Exploration Innovation Hub Center Space Exploration Experiment Building

JAXA Space Exploration Innovation Hub Center.

The Space Exploration Field at the JAXA Sagamihara Campus is a 400 square meter indoor sand field with controlled lighting and climate in which full-size rovers and landers are driven, dropped and operated [1]. It occupies the Space Exploration Experiment Building, which is run by the Space Exploration Innovation Hub Center. Both English names are translations: JAXA publishes the building and the field only in Japanese, as 宇宙探査実験棟 and 宇宙探査フィールド [1][2]. It was completed in February 2017 and entered service in May 2017. The building sits alongside the older ISAS Sagamihara test buildings, which provide structural, vibration, thermal vacuum, anechoic and drop-test capability at component and spacecraft scale [3].

Laboratory data

Parameter	Value
Operator	JAXA Space Exploration Innovation Hub Center, known as TansaX [1][3]
Location	Sagamihara Campus, Chuo-ku, Sagamihara, Kanagawa, Japan
Commissioned	Building completed February 2017, operational May 2017 [2]
Type	Indoor analogue terrain field with controlled illumination and climate [1]
Floor area	Gross floor area 1232.76 m2; building area 899.83 m2; field 400 m2 [1][2]
Capabilities	Field, control rooms, cleanroom
Simulant or terrain	Silica sand, 425 t: 410 t at 0.3 to 0.6 mm, 15 t at 3 to 5 mm
Instrumentation	Two control rooms, a catwalk, a 2.8 t indoor crane, xenon solar illumination
Ground truth	Not published. Users bring their own metrology
Fidelity limits	Ambient pressure, 1 g, room temperature; silica sand, not a simulant [1][5]. See below
Access	Open innovation and joint research with industry [1][2]. No lead time or fee published
Cited by	sora-q, lev-1

Capabilities

Space Exploration Field

Parameter	Value
Working volume	22.6 x 17.7 m, 400 m2, ceiling height 10.5 m [1]
Test article limits	Handling by a 2.8 t indoor crane [1][2]
Vacuum	Not applicable. Ambient pressure
Temperature	Controlled, not cycled. No range or ramp rate published
Illumination	Darkroom with a single xenon solar source [1]. No solar constant or collimation published
Simulant or terrain	Silica sand, 425 t, 0.3 to 0.6 mm and 3 to 5 mm, in flat, hill and gravel sections [1][2]
Slope	Piled by hand. 0 to 18 degrees used in a published campaign [5]. Maximum not published
Gravity offload	Not applicable
Instrumentation	Xenon solar illumination, catwalk, 2.8 t crane [1][2]. Users bring metrology

The field is the center of the building and is described by JAXA as reproducing lunar surface terrain and illumination conditions so that exploration robots and landers can be evaluated under conditions close to real operation [1]. The stated test types are surface driving, landing drop tests, flight tests and exploration work operation tests, run as a connected sequence rather than separately. JAXA attributes the field’s ability to take full-size landers and cooperative tests of several robots at once to its being among the largest in the world in both area and height.

Three design decisions define the envelope. The roof is a double folded insulated metal panel chosen to keep the interior temperature uniform against outside weather [2]. The ground under the field was improved into a strong bearing layer to support 425 tonnes of sand, and the floor was built uniform across its whole area so that terrain can be piled into a hill or dug out like a well at any point, and so that it withstands the impact of a lander touchdown test. Temperature and humidity are managed so that the sand state and the lighting are identical from run to run [1]. No relative density target or preparation procedure between runs is published, and no solar constant fraction, collimation angle or achievable solar elevation is published for the xenon illumination.

Operations control rooms

Parameter	Value
Working volume	Two rooms adjoining the field and overlooking it [1][2]
Instrumentation	Laid out to simulate a three-point relay chain [2]

The two control rooms are laid out to stand in for a three-node relay, such as ground station, spacecraft interior and surface, or Earth, Moon and rover, rather than for a single operator position [2]. That makes operations latency and relay topology a testable variable alongside the terrain.

The second-floor viewing corridor gives a full view of the field for public visitors, and uses instantly switchable glass that changes from frosted to clear. JAXA states the switch is not only theatrical: it protects the intellectual property embodied in the hardware under test by making the field invisible on demand.

Cleanroom

Adjacent to the field, the Innovation Hub operates an ISO Class 1 cleanroom at Sagamihara, built for planetary protection work: comparing the sterilization and decontamination effectiveness and corrosion behavior of different techniques, building decontamination systems able to break down spores and biomolecules, extending inactivation to viruses and allergens where prior knowledge was thin, and developing the verification methods for all of it [4].

Instrumentation

Facility-supplied instrumentation published for the field is limited to the control rooms, the catwalk, the 2.8 tonne crane and the xenon solar illumination [1]. Campaign-specific metrology is brought by users. In the Tohoku University EX1 campaign the rover was tracked by a 16-camera OptiTrack system running at 180 Hz with plus or minus 0.15 mm accuracy, wheel speed came from encoders, and external cameras independently timed wheel rotations across a 2 m section so that average slip could be estimated without relying on the rover [5].

The neighboring ISAS buildings hold the environmental test capability the field does not: the Flight Environment Test Building carries the mechanical environment test room for vibration, shock and dynamic balance, plus a magnetic shield room, a space chamber, a radio anechoic chamber and a clean assembly room; the Structure and Mechanics Test Building tests strength and rigidity of structures and the function of interstage joints and fairings; and the Advanced Facility for Space Science and Technology holds wind tunnels, space plasma and cosmic radiation experiment facilities and a weightless drop test facility [3].

What it does not reproduce

The field trades environment for repeatability, and JAXA says so in those terms: the value claimed is that the sand state and the illumination are the same on every run and are not affected by weather, achieved through temperature and humidity control, a darkroom and artificial lighting [1]. Nothing in the published description offers vacuum, thermal cycling or reduced gravity in the field.

The soil is silica sand, 0.3 to 0.6 mm for the bulk of the mass and 3 to 5 mm for the gravel section [1], graded for handling and repeatability rather than matched to lunar mineralogy, and coarser than lunar regolith. A user group has published its view of the same class of material, that dry loose silica sand is a low-fidelity lunar regolith simulant whose sparse grain distribution makes sinkage and slip conditions more challenging than the real surface would [5].

Drop testing is bounded by the building. The floor was designed to withstand the impact of a lander touchdown test [2], which is a structural limit on the energy that can be delivered, and the 10.5 m ceiling bounds the drop height available [1].

Campaigns run there

SLIM and SORA-Q. JAXA states that the SLIM lander and the SORA-Q transformable lunar robot were tested in the Space Exploration Experiment Building, and the facility runs public tours built around that history [1]. See sora-q.

Lunar base construction machinery. Joint research on force-controlled construction machinery for lunar base building, with Yanmar Holdings, is run in the field, aimed at automatic and autonomous operation of construction equipment on the lunar surface [1].

Tohoku University EX1 high-speed rover campaign. A four-wheeled 21.63 kg rover of 0.82 by 0.52 by 0.67 m with a passive spring-damper suspension was driven over a 20 m by 20 m area of silica sand about 0.3 m deep, at wheel velocities of 0.23 to 1.17 m/s on flat ground and on slopes of 0 to 18 degrees at up to 0.47 m/s, with additional rapid acceleration and deceleration runs to capture transient slip [5]. The resulting slip and sinkage regressions were fitted for use in a real-time lunar surface simulator. The campaign also established that grouser length has to be included in the effective wheel radius or the computed slip comes out negative during normal driving [5].

References