Hayabusa 2 (Хаябуса-2), Procyon – H-IIA F26 – Танэгасима – 03.12.2014 04:22:04 UTC

Автор Космос-3794, 13.08.2010 10:49:07

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tnt22

http://www.hayabusa2.jaxa.jp/en/topics/20180828e/index.html
ЦитироватьHow the Star Tracker image of Ryugu was used for optical navigation

Notice: This is an English translation of the Japanese article on May 25, 2018.

Fr om May 11 - 14, asteroid Ryugu was imaged using the Star Tracker onboard Hayabusa2. This data was then used for the application of optical navigation towards the asteroid in this mission.

Around May 20, 2018, Hayabusa2 was about 287 million km fr om the Earth (see Figure 1) and about 40,000 km fr om Ryugu (Figure 2). The exact size of Ryugu is currently unknown, but the diameter is estimated to be around 900 m. This means that it is necessary to arrive at a target of 900 m fr om a distance of about 300 million km travelling from Earth. Such precision requires optical navigation. (For comparison, a 900 m target at a distance of 300 million km is the same as a 6 cm target at a distance of 20 thousand km. This is equivalent of aiming at a 6 cm target in Brazil from Japan.)
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Figure 1: The location of Hayabusa2 on May 20, 2018, relative to other celestial bodies projected onto the ecliptic plane. The vernal equinox occurs when the Earth is at the right-side of the Sun and celestial bodies revolve around the Sun counter clockwise.


Figure 2: Location of Hayabusa2 and Ryugu on May 20, 2018. This figure shows the vicinity of Ryugu in Figure.1.

The orbit of a planetary explorer like Hayabusa2 is usually estimated by communicating with the spacecraft via radio waves. The technical term for this method is RARR: Range And Range Rate. "Range" is the distance from the Earth to the spacecraft and is calculated by measuring the round-trip propagation time of radio waves sent from Earth to the spacecraft and back.

"Range rate" is a measurement of the velocity of the spacecraft along the line-of-sight: along the direction to the spacecraft when viewed from Earth. It is calculated from the change in frequency of the transmitted and received radio waves. This effect is commonly known as the "Doppler Effect" and is experienced every time a loud vehicle such as an ambulance passes you on the street. As the ambulance approaches, the sound waves from the siren get bunched together, which increases the frequency of the wave and raises the pitch. When the ambulance retreats into the distance, these sound waves are stretched and their frequency decreases, lowering the pitch. Measuring this frequency change would allow you to estimate the velocity of the ambulance. Likewise, the change in the radio wave frequency from Hayabusa2 allows us to measure the velocity of the spacecraft.

The RARR method can measure the spacecraft's position at 300 million km away to around 300 km. But this is not good enough to arrive safely at Ryugu!

For Hayabusa2, we can use an orbit estimation method called DDOR in addition to RARR. DDOR stands for "Delta Differential One-way Range" and can also be referred to as "relative VLBI", wh ere VLBI is "Very Long Baseline Interferometry". Unlike RARR, DDOR uses two different antennas at widely separated Earth ground stations to receive radio waves from the spacecraft. The difference between the times measured for the radio waves to reach to each station can be used to obtain a more accurate estimate of the spacecraft position. Ideally, this time difference would depend only on the distance between the ground stations. However, delays can also occur due to variations in the Earth's atmosphere. To compensate for this, very distant radio-emitting celestial objects known as "quasars" are also observed. Any distortion due to atmospheric and ionospheric (the upper part of the Earth's atmosphere) can be subtracted from the signal from the spacecraft to get the probe's true distance. DDOR allows the position of Hayabusa2 at 300 million km to be measured to a precision of about several kilometres.

The DDOR measurement for the position of Hayabusa2 is excellent, but there is also uncertainty in the measured position of Ryugu. Since Ryugu cannot transmit radio waves to Earth (and is too distant to allow radio waves to be reflected via radar), DDOR cannot be used to gauge its position. On May 2018, the position of Ryugu was estimated to within 220 km. This means that even if the position of Hayabusa2 can be estimated to within a few kilometres, it would still not be possible to arrive at Ryugu.

This is why we need to use optical navigation. Optical navigation uses knowledge of the direction of Ryugu from the spacecraft to estimate more precisely wh ere the asteroid currently is on its orbit. This is then used to improve the predicted trajectory of Ryugu. To acquire the direction, Ryugu is photographed using a camera onboard Hayabusa2, producing an image containing both the asteroid and background stars. The position of the background stars is precisely known, allowing the direction to Ryugu to be measured. Optical navigation was employed when Ryugu was imaged using the Star Tracker, an instrument usually employed to estimate the orientation of the spacecraft.

A schematic diagram of how finding the direction to Ryugu improves knowledge of the asteroid's trajectory is shown in Figure 3. The blue oval shows the original region prior to optical navigation wh ere Ryugu could potentially lie. By knowing the direction of Ryugu with respect to the background stars, that error range can be shrunk to that indicated by the red brackets. This allows Ryugu's future trajectory to be known with greater precision as Hayabusa2 continues to approach the asteroid.

When we do this in practice, we are able to simultaneously analyze the radio wave and optical navigation data to estimate the orbits of both Hayabusa2 and Ryugu.


Figure 3: The principal of optical navigation by Hayabusa2.

Let's look at how well this works in practice with the images of Ryugu taken by the Star Tracker. Figure 4 is the starry sky seen from Hayabusa2, wh ere Ryugu's expected position over the course of about a week is shown by the line. The orange and green lines and points show the estimated path of Ryugu before and after the trajectory of the probe and asteroid was improved via optical navigation. Yellow points show the actual observed position of Ryugu. On the scale of Figure 4, the expected orbital path of Ryugu before and after optical navigation overlap with the actual observations, so it is not possible to see how much optical navigation improved the predictions.


Figure 4: Results of the optical navigation with the Star Tracker. Orange: Expected position of Ryugu seen from the spacecraft calculated from orbital information prior to using optical navigation. Green: Expected position of Ryugu calculated with greater accuracy using optical navigation data. Yellow: The direction of the observed Ryugu.

In Figure 5, we enlarged the observed area around the 5/13 (May 13) point in Figure 4. In this figure, the expected position and trajectory of Ryugu before and after the optical navigation data was used are plotted along with the observation of Ryugu at that time. The deviation from the true location of Ryugu is much smaller after collecting the optical navigation data.


Figure 5: The effect of optical navigation. This is an enlarged region of Figure 4, centered around the position of Ryugu observed on 5/13. Also shown is the estimate of the asteroid's orbit and position at this time using data before and after optical navigation was employed. The trajectory estimated using optical navigation is closer to the true observation of position.

After the use of optical navigation in May, the uncertainty in the spacecraft position was 3 km, and the uncertainty in the position of Ryugu was 130. This error was still large, but it was not a problem. During this use of optical navigation for Hayabusa2, the spacecraft was still using its ion engines, so the optical navigation result was being used to determine the direction and magnitude of this thrust. At the beginning of June, the period of ion engine operation ends and more precise optical navigation using the onboard Optical Navigation Camera (ONC) will begin. This will ensure our arrival at Ryugu.

※ Hayabusa Flash-back Corner

Hayabusa --our first mission to the asteroids-- also used optical navigation before arrival at asteroid Itokawa. As with Hayabusa2, the first step was an image taken with the Star Tracker. The article (in Japanese) reporting this event on August 15, 2005 can be found here.

The situation for Hayabusa was slightly different to that for Hayabusa2. For the Hayabusa mission, the uncertainty in the position of asteroid Itokawa was smaller than that for Ryugu. This is because radar observations of Itokawa had been possible, allowing the trajectory to be predicted more accurately. Due to Ryugu not approaching the Earth close enough for radar observations since its discovery, the accuracy of the asteroid's orbit is not as good. On the other hand the accuracy of the trajectory of the actual spacecraft was far worse for Hayabusa than for Hayabusa2, as there was not the capacity to properly use DDOR. Therefore, to reach the small celestial body of Itokawa, whose size is only about 500 m, we had to use optical navigation to increase the accuracy of orbit predictions for Hayabusa.
[свернуть]
Hayabusa2 Project
2018.08.28

tnt22

http://www.hayabusa2.jaxa.jp/en/news/status/
ЦитироватьAug. 29, 2018

★ Hayabusa2 status(the week of 2018.8.20)★

The spacecraft is currently operating in BOX-B. On August 23, we announced to the media that the point denoted "L08" near the asteroid equator had been selected as the candidate site for the touchdown of Hayabusa2. However, the surface of Ryugu is covered with boulders, so we need to continue gathering and considering information so that we can touchdown safely. The MINERVA-II-1 and MASCOT lander decided to land at mid-latitude sites, N6 and MA-9. MINERA-II-1 separation is scheduled for September 21, and MASCOT on October 3. We are looking forward to seeing what kind of data these will collect!

2018.8.28 S.N.

tnt22

ЦитироватьJAXAウェブ‏Подлинная учетная запись @JAXA_jp 12 ч. назад

7月20・21日には、Box-C運用として高度約6kmまで降下したはやぶさ2。 その際ONC-T(望遠の光学航法カメラ)で撮影した小惑星リュウグウの画像を、 約30度おきに12枚掲載します。 はやぶさ2の着地候補地点の位置が、より理解しやすいかもしれません。

https://bit.ly/2N3L5Wd 

#hayabusa2

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[свернуть]

tnt22

#403
http://www.hayabusa2.jaxa.jp/topics/20180831/
(вольный) пер. с яп.
ЦитироватьИзображение Рюгю, сфотографированное в режиме Box-C

С 20 по 21 июля Сокол-2 спусткался примерно до 6 км над уровнем поверхности астероида во время режима Box-C. Здесь приведены некоторые из изображений, опубликованных ранее в статье от 25 июля и в статье от 31 июля. Кроме того, на приводимые изображения наложены области-кандидаты на касание и посадки.

Ниже размещены 12 снимков, сделанных в ONC-T (оптической навигационной камерой - телескопической) в режиме Box-C с интервалом примерно 30 °. Для справки также указываются элементы, описывающие положение области выбора места посадки в соответствии с общим снимком, приведённым на рисунке 1 ниже.


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Рисунок 1 Позиции областей-кандидатов качания и приземления на фотографии поверхности Рюгю. Область, обозначенная как L08, является кандидатом на касание, а L07 и M04 - резервные. MA-9 - ожидаемая посадочная площадка MASCOT, N6 - планируемая зона посадки MINERVA-II-1. (© JAXA, Токийский университет, Университет Кочи, Университет Риккио, Университет Нагоя, Технологический институт Чибы, Университет Мэйдзи, Университет Айзу)

На приводимых ниже изображениях обратите внимание на их ориентацию. На рис.1 север Рюгю вверху. Это направление противоположно ранее показанным изображениям (статья 25 июля и статья 31 июля). Север Рюгю направлен к Антарктиде на Земле. Это связано с тем, что Рюгю вращается в противоположном направлении относительно Земли.

 
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Изображение 1 Съемки сделаны 20 июля 2018 года 07:12 (UTC)
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Изображение 12 Съемки сделаны 20 июля 2018 года 14:28 (UTC)
[свернуть]
Благодарности ※: JAXA, Токийский университет, Университет Кочи, Университет Риккио, Университет Нагоя, Технологический институт Чиба, Университет Мэйдзи, Университет Айзу

...

Проект Hayabusa 2
2018.08.31

Юрий Темников

Интересно практически полное отсутствие свежих ударных кратеров при огромном количестве камней и пыли.
Вначале было СЛОВО!И Такое......что все галактики покраснели и разбежались.

hlynin

JAXA, Кандидаты на посадочные площадки для миссии Hayabusa2 (JAXA, Candidates for landing sites for the Hayabusa2 mission) (на японском и английском языках) 23.08.2018 в pdf - 1,50 Мб
 0. Hayabusa-2 и план текущей миссии
 1. Статус проекта и общий график
 2. Кандидаты на место и ожидаемые даты
 3. Выбор кандидатур на приземление
 4. Научные дискуссии для кандидатур на приземление
 5. Выбор кандидатур на место посадки для MASCOT
 6. Выбор кандидатур на место посадки для MINERVA-II
 7. Стратегия успешного приземления
 8. Планы на будущее

tnt22

ЦитироватьAnimation: Asteroidlander MASCOT on board Hayabusa2

DLR

Опубликовано: 16 мая 2018 г.

On 3 December 2014, the Japanese space probe Hayabusa2 embarked on a sample return mission to asteroid (162173) Ryugu (formerly designated 1999 JU3). On board is the Mobile Asteroid Surface Scout (MASCOT), a lander built by the German Aerospace Center (Deutsches Zentrum für Luft-und Raumfahrt; DLR) in collaboration with the French space agency CNES. The aim of the Hayabusa2 mission is to learn more about the origin and evolution of the Solar System. As asteroids account for some of the most primordial celestial bodies, researching them gives us a glimpse into our cosmic past. Furthermore, Ryugu is a near-Earth asteroid, which means it could pose a threat to Earth and must be investigated in order to reduce this threat.
https://www.youtube.com/watch?v=8H4aZX_8hMAhttps://www.youtube.com/watch?v=8H4aZX_8hMA (7:14)

tnt22

Уже традиционный брифинг JAXA о текущем состоянии дел на астероиде Рюгю. Прямая трансляция JAXA 5 сентября с 11:00 до 12:00 (JST)
Цитировать

02:00 - 03:00 UTC
05:00 - 06:00 ДМВ

tnt22

http://www.hayabusa2.jaxa.jp/en/topics/20180904e/
ЦитироватьDetermination of landing site candidates!

The Landing Site Selection (LSS) conference was held on August 17, 2018 and the candidate landing locations for touchdown, MASCOT and MINERVA-II-1 on the surface asteroid Ryugu were decided. In this article, we introduce the landing candidate spots and the planned dates for these surface operations, along with details of the selection.

Figure 1 is a map of asteroid Ryugu showing the landing candidate locations. Please note the direction of north and south on this map (Note).


Figure 1: Candidate landing sites. 
Image credit for the map of Ryugu ※: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University. University of Aizu, AIST.
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The areas within the colored lines in Figure 1 are the candidate areas for the landing sites for the touchdown of the Hayabusa2 mothership (for sampling), MASCOT and MINERVA-II-1. These are labelled as:
Touchdown:L08 (backup sites: L07, M04)
MASCOT:MA-9
MINERVA-II-1:N6
L08 is the first choice (primary) candidate for the mothership's touchdown, with L07 and M04 as back-up options. The designation "L" and "M" refer to low latitude (L) and mid-latitude (M) positions. The "L" candidate positions were sel ected fr om among 13 preliminary candidate sites, while the "M" location was chosen from a set of four candidate sites. The size of the site selection rectangles are approximately 100m. MA-9 was sel ected as the candidate landing site for MASCOT from ten possibilities, while the N6 candidate for MIENRA-II-1 was chosen fr om seven surface locations.

In Figure 2, each candidate region is shown on the ONC-T image taken during the BOX-C observations at an altitude of 6km. Also in this image, the top of the asteroid is the north pole (Note). Please do note this is the opposite to the publicly released images so far.

  
Figure 2: Candidate points marked on the image of Ryugu captured fr om an altitude of about 6km. The image was taken on July 20, 2018 by the Optical Navigation Camera – Telescopic (ONC-T).
Image credit ※: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu, AIST.

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Following the determination of the landing site candidates, the operation schedule is as follows:

[свернуть]
Hayabusa2 Project
2018.09.03

[Note] On the map shown in Figure 1, the north pole of the asteroid is on the top of the map. Public images released so far show the asteroid orientated in the opposite direction, with the direction of the Solar System's north (and for the Earth's North Pole) at the top. Geographical north and south of the asteroid is determined by rotation. As Ryugu rotates retrograde, in the opposite direction to the Earth and the Solar System, the asteroid's northern direction is reversed with respect to the Solar System. The situation is the same for Itokawa. An image with the asteroid's north at the top is therefore reversed compared to an image wh ere the Solar System north points upwards.

tnt22

http://www.hayabusa2.jaxa.jp/en/news/status/
ЦитироватьSep. 05, 2018

★ Hayabusa2 status(the week of 2018.8.27)★

Hayabusa2 has completed operation in BOX-B; observing the asteroid while moving laterally up to 9km while remaining at an altitude of about 20km. As the first rehearsal for touchdown is scheduled to start on 09/11, the spacecraft is now returning to the descent start position. In the first touchdown rehearsal, the spacecraft will descend to 30m or less from the asteroid surface to acquire a more detailed image of the primary touchdown candidate point, L08, and the surroundings. The distance to the asteroid will be measured for the first time using the LRF (Laser Range Finder); a short-distance laser sensor that is used for touchdown. This will be the first time the LRF has been used to measure distance since launch.

2018.09.04 F.T.

tnt22

Была яп. версия статьи в русском вольном переводе.

Англ. официальный вариант

http://www.hayabusa2.jaxa.jp/en/topics/20180905e/
ЦитироватьImages of Ryugu captured during BOX-C operations

On July 20 – 21, 2018, the Hayabusa2 spacecraft descended to an altitude of about 6km as part of the BOX-C operation. We introduced a few of the images taken at this time in articles on July 25 and July 31. The articlediscussing the selection of the candidate landing sites also indicates the locations using BOX-C images.

In this post, we show 12 images taken with the ONC-T (Optical Navigation Camera – Telescopic) during the BOX-C operation at approximately 30 degree intervals. We show the original images and the images marked with the landing site candidates below, starting with the complete set of candidates in Figure 1.


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Figure 1: Candidate landing sites marked on the photograph of the surface of Ryugu. The area labelled L08 is the candidate touchdown site, with L07 and M04 as back-up locations. MA-9 is the anticipated landing area of MASCOT, while N6 is the scheduled landing area for MINERVA-II-1. (credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University. University of Aizu, AIST.)
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The images of the asteroid during the BOX-C operation are shown below, but please pay attention to the image orientation. In both the following and in Figure 1, the north pole of asteroid Ryugu is at the image top. In previous articles on July 25 and July 31, the orientation of this image was reversed. The north pole of Ryugu points in the same direction as the south pole on Earth, as Ryugu rotates in the opposite direction to our planet.

ЦитироватьПрим. Из-за особенностей движка форума изображения не помещаются плечом к плечу,только одно под другим. Поэтому левым снимкам статьи соответствуют верхние снимки, а правым - соответственно, нижние
  
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Image 1 taken on July 20, 2018 at 07:12 UTC

 
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Image 2 taken on July 20, 2018 at 07:52UTC.

 
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Image 3 taken on July 20, 2018 at 08:31UTC.

  
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Image 4 taken on July 20, 2018 at 09:11UTC.

 
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Image 5 taken on July 20, 2018 at 09:51UTC.

 
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Image 6 taken on July 20, 2018 at 10:30UTC.

 
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Image 7 taken on July 20, 2018 at 11:10UTC.

 
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Image 8 taken on July 20, 2018 at 11:49UTC.

 
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Image 9 taken on July 20, 2018 at 12:29UTC.

 
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Image 10 taken on July 20, 2018 at 13:09UTC.

 
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Image 11 taken on July 20, 2018 at 13:48UTC.

 
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Image 12 taken on July 20, 2018 at 14:28UTC.

Image credit ※: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University. University of Aizu, AIST

※ Please use the displayed credit when reproducing these images. In the case where an abbreviated form is necessary, please write "JAXA, University of Tokyo & collaborators".
[свернуть]
Hayabusa2 Project
2018.09.05

tnt22

https://spaceflightnow.com/2018/09/06/hayabusa-2-team-sets-dates-for-asteroid-landings/
ЦитироватьHayabusa 2 team sets dates for asteroid landings
September 6, 2018 | Stephen Clark


Hayabusa 2's optical navigation camera captured this view of asteroid Ryugu fr om a distance of 6 kilometers (4 miles) on July 20. Credit: JAXA

Japan's Hayabusa 2 spacecraft is preparing to release three hopping robots to land on asteroid Ryugu in the coming month, with tiny instruments scientists hope will explore the airless world's boulder-strewn landscape and return the first images from the surface of an asteroid.

Two of the landers developed by the Japanese space agency will be deployed together by Hayabusa 2 on Sept. 21, and another landing probe provided by German and French scientists is set for its descent to Ryugu on Oct. 3.

Those landing attempts will be preceded by a landing rehearsal using the Hayabusa 2 spacecraft to approach within 100 feet (30 meters) of Ryugu next week. The spacecraft is scheduled to reach its closest point to the asteroid Sept. 12, low enough to fire and test its laser range finder, a navigation sensor to be used on future touch-and-go maneuvers to snag a sample of Ryugu for return to Earth.

Next week's practice descent will set the stage for a second rehearsal in mid-October

The close-up maneuvers around Ryugu come after more than two months of mapping surveys, revealing Ryugu's appearance for the first time after Hayabusa 2's arrival in late June.

The mission's early reconnaissance of Ryugu allowed scientists to measure its size and mass. The asteroid has a slightly flattened shape, spanning around 1,640 feet (500 meters) in diameter along its equator and approximately 1,440 feet (440 meters) from pole-to-pole.

Ryugu makes one rotation every 7.63 hours and has a mass of roughly 450 million metric tons (496 million tons), yielding a calculation of the asteroid's gravity.
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Scientists developed this shape model of asteroid Ryugu using data from Hayabusa 2's laser altimeter instrument. Credit: JAXA

Scientists say Ryugu is a C-type asteroid, suggesting it contains primitive building blocks left over the formation of the solar system 4.5 billion years ago. Managed by the Japan Aerospace Exploration Agency, Hayabusa 2 will bring back specimens of the asteroid's primordial surface for analysis in sophisticated laboratories on Earth.

Hayabusa 2's deployable asteroid landers will make a leisurely descent to Ryugu after separation from the Hayabusa 2 mothership at an altitude of around 200 feet (60 meters). Ryugu's tenuous gravity — 80,000 times weaker than Earth's gravity field — will gently tug on the landing probes as they make an uncontrolled free fall to the asteroid, reaching the surface at a speed of less than 1 mph (about 30 centimeters per second).

The first pair of landers to be released Sept. 21 by Hayabusa 2 are carried inside the same container. The MINERVA-II robots, which each weigh a little more than 2.4 pounds (1.1 kilograms), are designed to hop across Ryugu, using cameras, thermometers and other sensors to investigate Ryugu from the surface.

Developed by JAXA, the disk-shaped MINERVA-II landers each have a diameter of 6.7 inches (17 centimeters) — less than the width of a typical dinner plate — and stand around 2.7 inches (7 centimeters) tall. The Hayabusa 2 mothership will put the landers on a trajectory to touch down in Ryugu's northern hemisphere.

A third MINERVA-II lander carried by Hayabusa 2 is set to be released for a landing on Ryugu next year.


Artist's illustration of the MINERVA-II robots carried by Hayabusa 2. The two probes depicted on the left side of the image will be released Sept. 21. Credit: JAXA

The mission's largest landing craft is MASCOT — the Mobile Asteroid Surface Scout — a joint project by the German and French space agencies. It's due to be released by Hayabusa 2 on Oct. 3.

Conceived and designed by the same team that developed the Philae lander, which made the first soft landing on a comet in 2014, the MASCOT spacecraft will bounce to a rest on Ryugu somewh ere in the asteroid's southern mid-latitudes.

"It's a very small lander," said Tra-Mi Ho, MASCOT's project manager at DLR, the German space agency. It's not bigger than a shoebox, and its weight is not more than 10 kilograms (22 pounds)."

The MASCOT lander "carries four scientific instruments," Ho said. "There is a wide-angle camera called MASCAM. It is there to determine the geology — the means to investigate the surface features of Ryugu — and for that it will require imaging at multiple wavelengths.

"We have got a microscope," Ho said in an Aug. 23 press briefing in Japan. "It's a spectral microscope provided by CNES (the French space agency). It is determining the mineralogy. It determines also the content of organic materials and hydrated minerals on the surface — of the water — by investigating the spectral features.

"We have a got a thermal radiometer," Ho continued. "It is called MARA. MARA is detecting or investigating the surface temperature of the asteroid. We have got a magnetometer as well, which is called MASMAG. It is there to determine if a magnetic filed exists in the asteroid or in the boulders."


A technician installs the MASCOT lander into the Hayabusa 2 spacecraft before launching to an asteroid. Credit: DLR

Billed by European scientists as Philae's "little brother," MASCOT carries a self-righting mechanism to orient itself after settling down on Ryugu's surface. The autonomous lander will also try to hop to different positions on the asteroid during its planned 16-hour mission, which is limited by the capacity of the probe's battery.

Ground teams carefully analyzed imagery and science data from Hayabusa 2 to sel ect candidate landing sites for the MINERVA-II and MASCOT spacecraft.

Scientists wanted to ensure none of the landers end up near Hayabusa 2's sampling target, located near Ryugu's equator, and assessed numerous candidate landing sites to find locations relatively free of large boulders. Managers also considered temperature and communications constraints — all the landers have thermal limits and must relay data back to Earth through Hayabusa 2.

MASCOT science team members ranked their candidate landing sites during an Aug. 14 meeting in Toulouse, France, and briefed their proposal to Hayabusa 2 officials in Japan the following week. The teams announced the landing site selections for the MINERVA-II and MASCOT robots, along with the first of up to three sampling sites for Hayabusa 2, during a press conference Aug. 23.

But despite the diligence by engineers and scientists on Earth, the miniature landers must function in an extreme environment, with temperature swings and an asteroid surface marked with numerous boulders that could pose danger for the tiny robots.

"Ryugu seems to be very homogeneous, so you have got more or less the same composition everywhere," Ho said. "Although we are happy, I think I will have sleepless nights until October," she said. "Until we land there, we still don't know how it looks exactly at the landing site ... So the unknown boulder size distribution at the site, which is critical for MASCOT, is still imposing a risk for our mission."


Members of the MASCOT, Hayabusa 2 and MINERVA-II teams (left to right) point out their landing sites. Credit: JAXA

MASCOT was powered on for testing after Hayabusa 2's arrival at Ryugu, confirming the robot survived its interplanetary cruise inside a carrier bay aboard the Japanese spacecraft. Hayabusa 2 launched on Dec. 3, 2014, and completed its nearly 2 billion-mile (3.2 billion-kilometer) journey to the asteroid June 27.

"MASCOT has been designed to be robust for launch, and on the asteroid, especially for landing," Ho said. "If you consider the MASCOT landing, it's like you drop MASCOT at roughly (a couple of inches) onto a table. So we think, from an impact point of view, it should be robust.

"However, we do not know how the asteroid looks," Ho said. "So, for example, a very unfortunate (scenario) is MASCOT finally settles between two rocks, and it might be trapped."

Hayabusa 2's nano-landers will not be the first spacecraft to achieve a soft landing on an asteroid. That distinction goes to NASA's NEAR-Shoemaker mission, which made a controlled touchdown on asteroid Eros in 2001 and unexpectedly continued beaming science data back to Earth.

But NEAR-Shoemaker did not return any asteroid images fr om the surface of Eros, leaving that "first" in space exploration up for grabs by MINERVA-II and MASCOT.

The Japanese-built MINERVA-II landers are based on a similar craft that flew with Japan's Hayabusa mission to asteroid Itokawa, but that landing attempt was unsuccessful.

Hayabusa 2 is one of two sample return missions that are beginning their asteroid exploration campaigns this year. NASA's OSIRIS-REx mission is scheduled to arrive at asteroid Bennu on Dec. 3, culminating in its own touch-and-go sample grab in mid-2020.

Hayabusa 2 is set to depart the asteroid in late 2019, with return to Earth scheduled for December 2020 with a parachute-assisted landing of the mission's sample carrier in Australia.
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Сайт работ на Соколе-2 в реальном времени открыт теперь и на англ.яз.

ЦитироватьHAYABUSA2@JAXA‏ @haya2e_jaxa 4 ч. назад

Curious about what Hayabusa2 is doing right now? Our Haya2Now website is now in English! Just rollover each panel to find out more:

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http://www.hayabusa2.jaxa.jp/en/topics/20180907e/
ЦитироватьThermography of Ryugu by the TIR

We conducted observations of asteroid Ryugu using the Thermal Infrared Imager (TIR) onboard Hayabusa2. Figure 1 shows the thermographic image taken using the TIR at an altitude of 20 km (the home position) fr om Ryugu.


Figure 1: Asteroid Ryugu observed with the Thermal Infrared Imager (TIR). The images were captured between 16:02 – 23:45 JST on June 30, 2018 and were taken every eight minutes for one rotation. From the 20 km altitude (home position), one pixel is about 20 m in size. The distance to the Sun at this time is 0.987 au (1 au is about 1.496 billion km, the average annular distance between the Sun and the Earth). The scale bar shows relative temperature (the values have no meaning). Red indicates a high temperature while blue is for colder temperatures.
Image credit ※: JAXA, Ashikaga University, Rikkyo University, Chiba Institute of Technology, University of Aizu, Hokkaido University of Education, Hokkaido Kitami Hokuto High School, AIST, National Institute for Environmental Studies, University of Tokyo, German Aerospace Center (DLR), Max Planck Society for the Advancement of Science, Stirling University.

The image shows the temperature differences on Ryugu's surface during one rotation, with red indicating regions with a high temperature. Distinct regions at different temperatures are captured by the TIR. Features in a thermal image can be seen even if they are in a shaded location in the visible photograph. This lets us confirm that the overall shape of the asteroid is well understood, and also the characteristic topography such as craters and large boulders that show up as a difference in temperature.

A temperature difference can also be seen between the north and south hemispheres of the asteroid. At present, it is summer in the southern hemisphere (the upper part of the figure) and the temperature is higher in this region. In the northern hemisphere in the lower part of the figure, it is currently winter and colder. This difference is due to the inclination of the rotation axis, which results in different levels of radiation reaching the north and south. The TIR has therefore spotted that asteroids also undergo a "seasonal change".

High temperatures on the asteroid reach 100°C, while the coldest regions sit at about room temperature. Temperatures also change depending on the solar distance of the asteroid, lowering as Ryugu moves further away from the Sun.

During the Hayabusa2 mission, we will investigate the formation process of asteroids by examining the characteristics of the surface material revealed by differences in surface temperature. From the TIR data, we can also look for scientifically important landing sites with millimeter-sized grains, and avoid landing Hayabusa2 in severe temperature environments or locations with obstacles such as boulders.

Reference: An article by Takehiko Arai, member of the TIR team, was posted on the Ashikaga University website (Japanese only).

※ Please use the displayed credit when reproducing these images. In the case wh ere an abbreviated form is necessary, please write "JAXA, Ashikaga University & collaborators".

Hayabusa2 project
2018.09.07

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JAXA выпустило материалы брифинга 05.09.2018 на англ. яз.

Hayabusa2_Press20180905_E_verL2.pdf - 2.7 MB, 30 стр, 2018-09-10 06:58:43 UTC