Полет АМС Dawn к Весте и Церере

[Georgij]

Про запас ещё Церера есть. Конечно, второго Энцелада не будет но думаю поинтереснее чем Эрос или Матильда

[Старый]

На снимке видно какой-то каньон. Разлом?

А левее-ниже него плато. Во смеху будет если поверхность окажется "изъеденой" как на Марсе!

[Georgij]

Об этом всем давно было известно. Большое количество метеоритов имеют происхождение с Весты, значит там должны быть кратеры. Просто думаю и кроме кратеров будет на что посмотреть

[Брабонт]

Во смеху будет если поверхность окажется "изъеденой" как на Марсе!

Почему? Вполне ожидаемо, если вспомнить богатую импактную историю Весты как родоначальницы семейства астероидов.

[Старый]

"Изъеденые местности" Марса это специфический вид местности - плато расчленённые эрозионными долинами на отдельные столовые горы, туда входят и хаосы. Во будет хохма если так окажется на Весте!

[Брабонт]

А, понял, о чём... Тем интереснее.

[pkl]

Про запас ещё Церера есть. Конечно, второго Энцелада не будет но думаю поинтереснее чем Эрос или Матильда

Церера? Это понятно. У неё, вроде, даже атмосферу находили. Можно и на ледяной вулканизм надеяться. А Веста, увы, слишком мала и слишком близка к Солнцу, чтобы на ней что-то интересное происходило. И, хотя я и надеялся на спутники, ничего особенного от неё не ожидал.

[pkl]

На снимке видно какой-то каньон. Разлом?

А левее-ниже него плато. Во смеху будет если поверхность окажется "изъеденой" как на Марсе!

И правее-выше тоже плато. Наверное, это одно образование, рассечённое каньоном.

[pkl]

Об этом всем давно было известно. Большое количество метеоритов имеют происхождение с Весты, значит там должны быть кратеры. Просто думаю и кроме кратеров будет на что посмотреть

А мне кажется, что кроме кратеров, там, в общем-то, ничего и нет. Будет как Лютеция - обглоданный метеоритами обломок.

[Salo]

http://www.youtube.com/watch?v=FsupRGBaFOA&feature=player_embedded

[Salo]

http://www.spaceref.com/news/viewsr.html?pid=37596

Dawn Status Report 1 July 2011[/size]

    Source: Jet Propulsion Laboratory
    Posted Saturday, July 2, 2011

Vesta beckons, and Dawn responds. Now more than halfway through its approach to Vesta, Dawn continues creeping up on the destination it has been pursuing since it began its interplanetary travels. The separation between them gradually shrinks as the probe's ion thrusting brings its orbit around the sun into a closer and closer match with Vesta's. At the same time, the giant protoplanet's gravity tugs gently on the approaching ship, luring it into orbit.

Starting at the beginning of the approach phase on May 3, Dawn interrupted thrusting once a week to photograph Vesta against the background stars. These images help navigators determine exactly where the probe is relative to its target. This technique does not replace other means of navigation but rather supplements them. One of the principal methods of establishing the spacecraft's trajectory relies on accurately timing how long it takes radio signals, traveling, as all readers know, at the universal limit of the speed of light, to make the round trip between Earth and Dawn. Another uses the Doppler shift of the radio waves, or the slight change in pitch caused by the craft's motion. These sensitive measurements remain essential to navigating the faraway ship as it sails the interplanetary seas.

Despite the very slow approach, the distance is small enough now that observing Vesta weekly is no longer sufficient. To achieve the navigational accuracy required to reach the intended orbit in early August, last week the frequency of imaging was increased to twice per week. In each session, half of the pictures are taken with long exposures to ensure many stars are detectable, thus overexposing the much brighter disc of the nearby Vesta. The other half use short exposures to ensure that the rocky world shows up correctly so its precise location can be measured. The visible and infrared mapping spectrometer has been commanded to observe Vesta during three of these sessions, each time providing valuable information that will help scientists select instrument settings for when Dawn is close enough to begin its detailed scientific measurements.

In addition to the regular campaign of imaging for navigation, mission controllers have other plans in store for the approach phase that were laid out more than a year ago. Twice in the next few weeks, the spacecraft will watch Vesta throughout its complete 5.3-hour rotation on its axis, revealing exciting new perspectives on this uncharted body. The explorer also will search for moons of the alien world.

There are several ways you can have the same spectacular views as Dawn while it closes in on this immense protoplanet. You could build your own ion-propelled interplanetary spaceship and travel to Vesta. Just imagine how exciting that would be! But if you did that, the time to write all the logs describing your adventure probably would make the undertaking impractical. Another option would be to build your own telescope. To see Vesta as clearly as Dawn sees it today, you would need a telescope only three times the size of the Hubble Space Telescope. Regrettably, then you would have to wait until Earth's and Vesta's orbits around the sun brought them into closer alignment. In the meantime, Dawn's camera would draw much closer to its subject. By the beginning of August, it will see Vesta with more than 100 times the clarity that Hubble could ever obtain. Still another alternative would be to go here to see some of the best views that humankind's robotic ambassador to the asteroid belt has returned. New pictures will be added regularly.

A relic that bears witness to the dawn of the solar system, a colossus that outweighs all other residents of the main asteroid belt save Ceres (Dawn's second destination), a fuzzy point of light among the stars that has intrigued and enticed astronomers for more than two centuries, a mysterious orb that has stirred the passions of creatures on a distant planet, inspiring them to dispatch an emissary to scrutinize it, is finally being revealed as a unique and fascinating world. Dawn's images delight and tantalize us, and the wait for still better views now is brief indeed.

After more than 950 days of ion thrusting, with an effective change in velocity of more than 6.6 kilometers per second (15,600 mph), Dawn's orbit is so much like Vesta's that their paths around the sun are quite similar. Less than a month ago, they were coming together at 240 meters per second (540 mph). Today, the relative speed has declined to only 110 meters per second (250 mph). By July 16, Dawn will be traveling no faster toward Vesta than you can drive in a car. The probe will be close enough and slow enough that the protoplanet's gravity will tenderly take the approaching explorer in its grasp. The next log will be posted shortly after Dawn is in a high, loose orbit around Vesta, still spiraling down toward survey orbit, where it will begin making detailed studies of its home for the subsequent year.

Dawn is 152 thousand kilometers (95 thousand miles) from Vesta, or 40 percent of the average distance between Earth and the moon. It is also 1.39 AU (208 million kilometers or 129 million miles) from Earth, or 515 times as far as the moon and 1.37 times as far as the sun today. Radio signals, traveling at the universal limit of the speed of light, take 23 minutes to make the round trip.[/size]

[Athlon]

Об этом всем давно было известно. Большое количество метеоритов имеют происхождение с Весты, значит там должны быть кратеры. Просто думаю и кроме кратеров будет на что посмотреть

А мне кажется, что кроме кратеров, там, в общем-то, ничего и нет. Будет как Лютеция - обглоданный метеоритами обломок.

Да, Церера судя по всему поинтереснее будет. Будем надеяться, что Dawn до нее долетит.

[pkl]

Об этом всем давно было известно. Большое количество метеоритов имеют происхождение с Весты, значит там должны быть кратеры. Просто думаю и кроме кратеров будет на что посмотреть

А мне кажется, что кроме кратеров, там, в общем-то, ничего и нет. Будет как Лютеция - обглоданный метеоритами обломок.

Да, Церера судя по всему поинтереснее будет. Будем надеяться, что Dawn до нее долетит.

Мы точно знаем, что она сферична. Мы точно знаем, что на ней вода. Предположительно, у неё периодически возникает атмосфера. Конечно, она обещает быть интересней! В общем, если Веста - это очень большой астероид, то Церера - это маленькая планета. Я думаю, возобновятся и споры, что есть астероид, а что - планета. Видимо, граница проходит как раз между ними.

[instml]

http://neo.jpl.nasa.gov/orbits/fullview4.jpg

Осталось 50 тысяч км.

[instml]

Does Asteroid Vesta Have a Moon?
http://science.nasa.gov/science-news/science-at-nasa/2011/06jul_vestamoon/

[Чебурашка]

http://neo.jpl.nasa.gov/orbits/fullview4.jpg

Осталось 50 тысяч км.

Судя по картинке, относительная скорость - 70 м/c
А 2-ая космическая скорость для Весты на таком расстоянии (если оценки массы Весты верны) - 27 м/c.
Осталось погасить совсем немного скорости до зазхвата.

[instml]

Image of Vesta Captured by Dawn on July 1, 2011

July 7, 2011 - PASADENA, Calif. -- NASA's Dawn spacecraft obtained this image with its framing camera on July 1, 2011. It was taken from a distance of about 62,000 miles (100,000 kilometers) away from the protoplanet Vesta. Each pixel in the image corresponds to roughly 5.8 miles (9.3 kilometers).
Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA


http://dawn.jpl.nasa.gov/multimedia/dawn_vesta_image_070111.asp

[sol]

окатыш какой-то

Веста все-таки шарик почти

[instml]

Dawn Team Members Check out Spacecraft

July 07, 2011

Dawn Mission Status Update

Mission managers for NASA's Dawn spacecraft are studying the spacecraft's ion propulsion system after Dawn experienced a loss of thrust on June 27. Dawn team members were able to trace the episode to an electronic circuit in the spacecraft's digital control and interface unit, a subsystem that houses the circuit and a computer that provides the "brains" to Dawn's ion propulsion system. That circuit appeared to lose an electronic signal. As a result, the valves controlling the flow of xenon fuel did not open properly. Dawn automatically put itself into a more basic configuration known as "safe-communications" mode, where the spacecraft stopped some activities and turned its high-gain antenna to Earth.

Engineers were able to return the spacecraft to a normal configuration and restart the spacecraft's thrusting on June 30 by switching to a second digital control and interface unit with equivalent capabilities. One set of images for navigation purposes was not obtained on June 28 because the spacecraft was in safe-communications mode, and one other set, on July 6, was not obtained to allow the spacecraft to spend the time thrusting. Other sets of navigation images have been and will be acquired as expected. The ion propulsion system is now functioning normally.

"Dawn is still on track to get into orbit around Vesta, and thanks to the flexibility provided by our use of ion propulsion, the time of orbit capture actually will move earlier by a little less than a day," said Marc Rayman, Dawn's chief engineer and mission manager. "More importantly, the rest of Dawn's schedule is unaffected, and science collection is expected to begin as scheduled in early August."

In an unrelated event, the visible and infrared mapping spectrometer on Dawn reset itself on June 29. At the time of the reset, the instrument was gathering calibration data during the spacecraft's approach to the giant asteroid Vesta. Some of its planned observations were completed successfully before automatic sensors turned the instrument off.

On June 30, Dawn team members were able to trace the reset to an internal error in the instrument's central processing unit, though they don't yet know why the internal error occurred. By temporarily turning the instrument back on, the Dawn team confirmed that the instrument is otherwise in a normal configuration. They powered the instrument back off, as originally planned for this time. Team members are working to determine when they will turn it back on again.

After arriving at Vesta, Dawn will spend about one year orbiting the asteroid, which is also known as a protoplanet because it is a large body that almost became a planet. Data collected at Vesta will help scientists understand the earliest chapter of our solar system's history.

The Dawn mission to Vesta and Ceres is managed by the Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate, Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala. The University of California, Los Angeles, is responsible for overall Dawn mission science. Other scientific partners include Planetary Science Institute, Tucson, Ariz.; Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany; DLR Institute for Planetary Research, Berlin, Germany; Italian National Institute for Astrophysics, Rome; and the Italian Space Agency, Rome. Orbital Sciences Corporation of Dulles, Va., designed and built the Dawn spacecraft.

To learn more about Dawn and its mission to the asteroid belt, visit: http://www.nasa.gov/dawn and http://dawn.jpl.nasa.gov .

http://www.jpl.nasa.gov/news/news.cfm?release=2011-206&rn=news.xml&rst=3063

[pkl]

окатыш какой-то

Веста все-таки шарик почти

Но всё же таки она достаточно массивная, чтобы "округлиться". А где суперкратер? С другой стороны?