MINERVA (spacecraft)
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MINERVA (MIcro-Nano Experimental Robot Vehicle for Asteroid) are a series of
rover Rover may refer to: People Name * Constance Rover (1910–2005), English historian * Jolanda de Rover (born 1963), Dutch swimmer * Rover Thomas (c. 1920–1998), Indigenous Australian artist Stage name * Rover (musician), French singer-songw ...
s developed by the Japanese space agency
JAXA The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into o ...
for the purpose of exploring
asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
surfaces. The first MINERVA was part of the ''
Hayabusa was a robotic spacecraft developed by the Japan Aerospace Exploration Agency (JAXA) to return a sample of material from a small near-Earth asteroid named 25143 Itokawa to Earth for further analysis. ''Hayabusa'', formerly known as MUSES-C ...
'' mission, and MINERVA-II are a series of three rovers for ''
Hayabusa2 is an asteroid sample-return mission operated by the Japanese state space agency JAXA. It is a successor to the ''Hayabusa'' mission, which returned asteroid samples for the first time in June 2010. ''Hayabusa2'' was launched on 3 December 2 ...
''. On 12 November 2005, MINERVA rover was deployed from Hayabusa orbiter with aim to land on asteroid
25143 Itokawa 25143 Itokawa (provisional designation ) is a sub-kilometer near-Earth object of the Apollo group and also a potentially hazardous asteroid. It was discovered by the LINEAR program in 1998 and later named after Japanese rocket engineer Hideo ...
. However, the landing failed as MINERVA missed the asteroid and ended up on heliocentric orbit. On 21 September 2018, first two MINERVA-II rovers successfully landed on asteroid
162173 Ryugu 162173 Ryugu ( provisional designation ) is a near-Earth object and also a potentially hazardous asteroid of the Apollo group. It measures approximately in diameter and is a dark object of the rare spectral type Cb, with qualities of both a ...
.They Made It! Japan's Two Hopping Rovers Successfully Land on Asteroid Ryugu
Meghan Bartels, ''Space.com''. 22 September 2018.
The third MINERVA-II rover malfunctioned before deployment from the Hayabusa2 orbiter, but it was released anyway on 2 October 2019 to perform gravitational measurements before impacting the asteroid a few days later.


Overview

Following the approval of the asteroid
sample-return A sample-return mission is a spacecraft mission to collect and return samples from an extraterrestrial location to Earth for analysis. Sample-return missions may bring back merely atoms and molecules or a deposit of complex compounds such as lo ...
project MUSES-C, a rover was proposed to be mounted on the asteroid explorer, and development of MINERVA began in 1997. Completed in February 2003, MINERVA was Japan's first space rover, and the first asteroid rover in the world. On 9 May 2003, the MUSES-C spacecraft carrying MINERVA was launched from
Kagoshima Space Center The is a space launch facility in the Japanese town of Kimotsuki, Kagoshima, Kimotsuki, Kagoshima Prefecture. Before the establishment of the Japan Aerospace Exploration Agency, JAXA space agency in 2003, it was simply called the (KSC). All o ...
, and was named ''
Hayabusa was a robotic spacecraft developed by the Japan Aerospace Exploration Agency (JAXA) to return a sample of material from a small near-Earth asteroid named 25143 Itokawa to Earth for further analysis. ''Hayabusa'', formerly known as MUSES-C ...
''. ''Hayabusa'' arrived at its target, asteroid
25143 Itokawa 25143 Itokawa (provisional designation ) is a sub-kilometer near-Earth object of the Apollo group and also a potentially hazardous asteroid. It was discovered by the LINEAR program in 1998 and later named after Japanese rocket engineer Hideo ...
, on 12 September 2005. After a two-month long observation phase, ''Hayabusa'' began descent rehearsals in preparation for its asteroid landings. On 12 November, MINERVA was separated from ''Hayabusa'' and headed for Itokawa, but the drop failed and thus MINERVA became the smallest artificial object in heliocentric orbit. Following separation MINERVA continued to communicate for 18 hours, transmitting data to its mothership. After ''Hayabusa'' return to Earth, a successor project, ''
Hayabusa2 is an asteroid sample-return mission operated by the Japanese state space agency JAXA. It is a successor to the ''Hayabusa'' mission, which returned asteroid samples for the first time in June 2010. ''Hayabusa2'' was launched on 3 December 2 ...
'', began, which also included a rover. While MINERVA was treated as an optional addition in the first Hayabusa, MINERVA-II became part of the nominal payload for ''Hayabusa2''. Launched on 3 December 2014, ''Hayabusa2'' arrived at asteroid
162173 Ryugu 162173 Ryugu ( provisional designation ) is a near-Earth object and also a potentially hazardous asteroid of the Apollo group. It measures approximately in diameter and is a dark object of the rare spectral type Cb, with qualities of both a ...
on 27 June 2018. MINERVA-II-1, composed of two identical rovers, was deployed from ''Hayabusa2'' in 21 September. Both rovers reached Ryugu's surface, and became the first probes ever to travel the surface of an asteroid. JAXA announced that the rovers have been named HIBOU (previously Rover-1A) and OWL (previously Rover-1B), respectively. The second rover deployment for MINERVA-II-2 happened 2 October 2019 16:38 UTC. The rover, known as Rover-2 or MINERVA-II-2 failed before deployment, but was released from the Hayabusa2 orbiter anyway to perform gravitational measurements. It impacted the asteroid a few days after release on 8 October.


Design


MINERVA

MINERVA consists of five components, including the rover's body. *OME-B, which mounts MINERVA to MUSES-C, and supplies power to MINERVA until its separation *OME-C, the cover between OME-B and MUSES-C *OME-E, the repeater between the mothership's data bus *OME-Ant, a flat
patch antenna A patch antenna is a type of antenna with a low profile, usually consisting of a printed circuit board. It consists of a planar rectangular or circular sheet or "patch" of metal, mounted over a larger sheet of metal called a ground plane. It ...
for OME-E to communicate with MINERVA These four components were inside the rover. MINERVA itself is a hexadecagonal prism with a diameter of 12 cm and a height of 10 cm, with solar cells attached to each side. This allows the probe to secure power in any attitude as long as it was in a sunlit environment. For shock mitigation during landing and to protect the solar cells, 16 pins are protruding from MINERVA's surface. Six among them had thermometers inside them to directly measure the asteroid's ground temperature. The pins also functioned as a means to increase friction during the hops. Power is supplied from the solar cells attached to every side of MINERVA. Surplus power gets stored in an
electric double-layer capacitor alt=Supercapacitor, upright=1.5, Schematic illustration of a supercapacitor upright=1.5, A diagram that shows a hierarchical classification of supercapacitors and capacitors of related types A supercapacitor (SC), also called an ultracapacitor, ...
, and is used in situations that requires greater power than what gets generated by the solar cells, such as rotating the motor and when using the cameras. After the electric double-layer capacitor ceases function, communication will still be possible but the rover will be unable to make further hops or imaging, so an operation was considered to have a stationary MINERVA continuously measure the asteroid surface temperature of its final resting place. Along with six built-in temperature sensors at the pins sticking out from the main body, MINERVA had three cameras and six
photodiode A photodiode is a semiconductor diode sensitive to photon radiation, such as visible light, infrared or ultraviolet radiation, X-rays and gamma rays. It produces an electrical current when it absorbs photons. This can be used for detection and me ...
s on board as external sensors. The three
CCD CCD may refer to: Science and technology * Charge-coupled device, an electronic light sensor used in various devices including digital cameras * .ccd, the filename extension for CloneCD's CD image file * Carbonate compensation depth, a property ...
cameras were identical; two of them faced the same direction and were adjacent with each other, enabling closeup stereographic imaging. This was intended for mainly shooting the asteroid surface. The remaining camera was placed on the opposite side of the two cameras, with the primary purpose of imaging the asteroid from above during the hops. On MINERVA's topside and underside an antenna is located. As the rover's attitude shifts, the either side facing Hayabusa was to be used. The communication speed between MINERVA and OME-E was  kbps, with a maximum range of 20 km. MINERVA has an on-board
microcomputer A microcomputer is a small, relatively inexpensive computer having a central processing unit (CPU) made out of a microprocessor. The computer also includes memory and input/output (I/O) circuitry together mounted on a printed circuit board (P ...
. Its main CPU
microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...
is
Hitachi () is a Japanese Multinational corporation, multinational Conglomerate (company), conglomerate founded in 1910 and headquartered in Chiyoda, Tokyo. The company is active in various industries, including digital systems, power and renewable ener ...
's SH-3, clocked at 10MHz, adopted for its low power consumption, performance efficiency and reliability. The computer's memory includes 2 MB
RAM Ram, ram, or RAM most commonly refers to: * A male sheep * Random-access memory, computer memory * Ram Trucks, US, since 2009 ** List of vehicles named Dodge Ram, trucks and vans ** Ram Pickup, produced by Ram Trucks Ram, ram, or RAM may also ref ...
, 512 KB
ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * ...
, and 2MB
Flash ROM Flash memory is an electronic non-volatile computer memory storage medium that can be electrically erased and reprogrammed. The two main types of flash memory, NOR flash and NAND flash, are named for the NOR and NAND logic gates. Both use ...
.


MINERVA-II-1

MINERVA-II-1 was developed by JAXA and the University of Aizu. It has a slim design compared to its predecessor, to increase the likelihood the surface with larger area would contact the asteroid surface. MINERVA-II-1 was enlarged from its predecessor as the rover's destination, asteroid Ryugu was more distant from the Sun than Itokawa, necessitating an increase in solar cell area. Ryugu's greater size compared to Itokawa means rovers will face stronger gravity, thus larger
DC motor A DC motor is an electrical motor that uses direct current (DC) to produce mechanical force. The most common types rely on magnetic forces produced by currents in the coils. Nearly all types of DC motors have some internal mechanism, either el ...
s are used for MINERVA-II-1. By deploying two rovers simultaneously, a network of space probes can be achieved. The maximum communication speed between the MINERVA-II-1 rovers and the mothership's OME-E is  kbps. The two rovers are nearly identical, the only difference being some internal sensors and the thermal characteristics. Rover-1A uses a traditional
multi-layer insulation Multi-layer insulation (MLI) is thermal insulation composed of multiple layers of thin sheets and is often used on spacecraft and cryogenics. Also referred to as superinsulation, MLI is one of the main items of the spacecraft thermal design, pri ...
, which covers the rover to prevent heat from entering, while Rover-1B is equipped with radiators to dissipate heat to the outside.


MINERVA-II-2

Unlike the other three MINERVAs (one on ''Hayabusa'', two on ''Hayabusa2'') developed by JAXA/
ISAS , or ISAS, is a Japanese national research organization of astrophysics using rockets, astronomical satellites and interplanetary probes which played a major role in Japan's space development. Established as part of the University of Tokyo ...
, MINERVA-II-2 was developed by a consortium of Japanese universities, and employs significantly different methods of mobility. MINERVA-II-2's primary goal is to verify navigation in an environment with extremely small gravitational acceleration. The rover was realized as an 'outreach payload', aimed at the university community. The responsibility of each universities are the following: *
Tohoku University is a public research university in Sendai, Miyagi, Japan. It is colloquially referred to as or . Established in 1907 as the third of the Imperial Universities, after the University of Tokyo and Kyoto University, it initially focused on sc ...
was responsible for overall management of ''Rover-2'', and developed a micro-hop type moving mechanism using micro vibrations *
Yamagata University is a national university located in the Japanese cities of Yamagata, Yamagata, Yamagata, Yonezawa, and Tsuruoka in Yamagata Prefecture. The Times Higher Education released Times Higher Education World University Rankings, World University Rank ...
developed an environmentally driven moving mechanism using
bimetal Bimetal refers to an object that is composed of two separate metals joined together. Instead of being a mixture of two or more metals, like alloys, bimetallic objects consist of layers of different metals. Trimetal and tetrametal refer to objects c ...
s *
Tokyo Denki University is a private university in Adachi, Tokyo, Japan. The predecessor of the school was founded in 1907 as . It was chartered as a university in 1949 with Yasujiro Niwa as first president. Denki (電機) means an electric device in Japanese, a ...
developed an internal impact type moving mechanism utilizing permanent magnets *
Osaka University The , abbreviated as UOsaka or , is a List of national universities in Japan, national research university in Osaka, Japan. The university traces its roots back to Edo period, Edo-era institutions Tekijuku (1838) and Kaitokudō, Kaitokudo (1724), ...
developed an elastic energy-releasing type moving mechanism using
leaf spring A leaf spring is a simple form of spring (device), spring commonly used for suspension (vehicle), suspension in wheeled vehicles. Originally called a ''laminated'' or ''carriage spring'', and sometimes referred to as a semi-elliptical spring, e ...
s *
Tokyo University of Science , formerly "Science University of Tokyo" or TUS, informally or simply is a private research university located in Shinjuku, Tokyo, Japan. History Tokyo University of Science was founded in 1881 as The Tokyo Academy of Physics by 21 graduate ...
developed the rover's on board cameras


Operation and landing


MINERVA (Hayabusa)

MINERVA was deployed by Hayabusa during the third landing rehearsal. On 12 November 2005 6:07:38 UTC the command to deploy MINERVA was sent from Earth. However, before the MINERVA deployment command, a command instructing Hayabusa to raise its altitude was accidentally sent. MINERVA was deployed on 6:24 UTC, but the distance to
25143 Itokawa 25143 Itokawa (provisional designation ) is a sub-kilometer near-Earth object of the Apollo group and also a potentially hazardous asteroid. It was discovered by the LINEAR program in 1998 and later named after Japanese rocket engineer Hideo ...
was 200 m, and Hayabusa was ascending at approximately 15 cm/s away from the asteroid. An image taken by Hayabusa 212 s after MINERVA's deployment caught both MINERVA and OME-C, the rover's cover that was also deployed. Of the images taken by MINERVA, only one was sent, which was a photograph of Hayabusa's solar panels. After separating from Hayabusa communication with MINERVA lasted for 18 hours.


MINERVA-II (''Hayabusa2'')

''Hayabusa2'' arrived at asteroid
162173 Ryugu 162173 Ryugu ( provisional designation ) is a near-Earth object and also a potentially hazardous asteroid of the Apollo group. It measures approximately in diameter and is a dark object of the rare spectral type Cb, with qualities of both a ...
on 27 July 2018. The spacecraft released MINERVA-II-1, a batch of 2 rovers, over the 'northern hemisphere' of Ryugu. The process was conducted fully autonomously, a countermeasure to prevent the recurrence of the error that doomed their predecessor. The landing site of MINERVA-II-1 rovers was named Tritonis. Of the two rovers, HIBOU (aka Rover-1A) took an image of ''Hayabusa2'' soon after deployment. OWL (aka Rover-1B) succeeded in recording a video from Ryugu. MINERVA-II-1 became the first probes to take an image, and move on an asteroid surface. After completing their missions, the two rovers will remain on the asteroid surface.


MINERVA-II-2

The MINERVA-II-2 rover, also called Rover-2, failed before deployment. It was however deployed 2 October 2019 on orbit around Ryugu to perform gravitational measurements. After release from Hayabusa2 it impacted the asteroid on 8 October.


See also

*
MASCOT A mascot is any human, animal, or object thought to bring luck, or anything used to represent a group with a common public identity, such as a school, sports team, university society, society, military unit, or brand, brand name. Mascots are als ...
* MMX rover *
Philae The Philae temple complex (; ,  , Egyptian: ''p3-jw-rķ' or 'pA-jw-rq''; , ) is an island-based temple complex in the reservoir of the Aswan Low Dam, downstream of the Aswan Dam and Lake Nasser, Egypt. Originally, the temple complex was ...


References


External links


Small rover MINERVA-II


* ttp://www.asahi.com/special/rocket/hayabusa2_3d/ ''Hayabusa2'' 3D model Asahi Shinbun {{Solar System probes Attached spacecraft Landers (spacecraft) Hopping spacecraft Planetary rovers