Category Archives: Asteroids & Comets

Asteroids & Comets, Space Science, Space Systems

Dawn snaps sharper images of Ceres

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Dwarf plane Ceres coming into focus as the Dawn spacecraft nears it:

Dawn Captures Sharper Views of Ceres

February 17, 2015 Image Advisory—Craters and mysterious bright spots are beginning to pop out in the latest images of Ceres from NASA’s Dawn spacecraft. These images, taken Feb. 12 at a distance of 52,000 miles (83,000 kilometers) from the dwarf planet, pose intriguing questions for the science team to explore as the spacecraft nears its destination.

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Two views of Ceres were acquired by NASA’s Dawn spacecraft on Feb. 12, 2015, from a distance of about 52,000 miles (83,000 kilometers) as the dwarf planet rotated. The images, which were taken about 10 hours apart, have been magnified from their original size. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

“As we slowly approach the stage, our eyes transfixed on Ceres and her planetary dance, we find she has beguiled us but left us none the wiser,” said Chris Russell, principal investigator of the Dawn mission, based at UCLA. “We expected to be surprised; we did not expect to be this puzzled.”

Dawn will be gently captured into orbit around Ceres on March 6. As the spacecraft delivers better images and other data, the science team will be investigating the nature and composition of the dwarf planet, including the nature of the craters and bright spots that are coming into focus. The latest images, which have a resolution of 4.9 miles (7.8 kilometers) per pixel, represent the sharpest views of Ceres to date.

The spacecraft explored the giant asteroid Vesta for 14 months during 2011 and 2012. Scientists gained numerous insights about the geological history of this body and saw its cratered surface in fine detail. By comparing Vesta and Ceres, they will develop a better understanding of the formation of the solar system.

Dawn’s mission to Vesta and Ceres is managed by the Jet Propulsion Laboratory for NASA’s Science Mission Directorate in Washington. Dawn is a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK, Inc., of Dulles, Virginia, designed and built the spacecraft. JPL is managed for NASA by the California Institute of Technology in Pasadena. The framing cameras were provided by the Max Planck Institute for Solar System Research, Gottingen, Germany, with significant contributions by the German Aerospace Center (DLR) Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The visible and infrared mapping spectrometer was provided by the Italian Space Agency and the Italian National Institute for Astrophysics, built by Selex ES, and is managed and operated by the Italian Institute for Space Astrophysics and Planetology, Rome. The gamma ray and neutron detector was built by Los Alamos National Laboratory, New Mexico, and is operated by the Planetary Science Institute, Tucson, Arizona.

The new Dawn images are available at the Ceres Science Gallery.

Asteroids & Comets, Space Science

New Rosetta images off Comet 67P/C-G

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New images of Comet 67P/C-G from the ESA Rosetta probe:

Last waltz at 28 km

This four-image mosaic comprises images taken from a distance of 28.7 km from the centre of Comet 67P/Churyumov-Gerasimenko on 3 February. The image resolution is 2.4 m/pixel and the individual 1024 x 1024 frames measure 2.5 km across. The mosaic has been slightly cropped, and it measures 4.2 x 4.6 km.

These are the last images taken by Rosetta’s NAVCAM before the spacecraft left its bound orbit around the comet at 28 km from the centre. On 4 February, Rosetta moved into a new operating phase characterised by a series of flybys past 67P/C-G at a range of distances, the first of which will be the very close encounter planned for next weekend, when Rosetta will pass just 6 km from the surface of the comet on 14 February.

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Four image mosaic comprising images taken on 3 February 2015 by Rosetta’s Navigation Camera (NAVCAM). Rotation and translation of the comet during the imaging sequence make it difficult to create an accurate mosaic, and there may be some spurious spatial and intensity features as a result of the mosaic-making sequence, so always refer to the individual frames before performing any detailed comparison or drawing conclusions about any strange structures or low intensity extended emission. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

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In this orientation, we see the smaller of the two comet lobes in the upper part of the image, with the larger lobe below. Emerging from the shadows of the comet’s neck are the cliffs of Hathor, in the central part of the image, crossing over to the Anuket region on the right. Parts of the smooth Hapi region on the neck are also visible in the shadows, just above the bright rim of the large lobe.

Some circular depressions on the Seth and Ash regions are visible on the large lobe; parts of the Anubis and Atum region can also be seen towards the lower right corner of the image.

The view of the small lobe shows mostly the Ma’at region, on the left, while the ridge on the right and the smooth plain above it belong to Serqet.

Asteroids & Comets

The search for the Philae lander on Comet 67P/C-G

Here is a reprint of an article from the Rosetta mission team on where the lander might be:

Where is Philae? When will it wake up?

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Where is Philae?

Ever since Philae touched down on Comet 67P/Churyumov-Gerasimenko for the final time on 12 November – it is thought to have come into contact with the comet’s surface a total of four times including the final landing – the search has been on to identify it in images. While the CONSERT instrument has helped to narrow down a 350 x 30 m ‘landing strip’ on Comet 67P/C-G’s smaller lobe, a dedicated search in OSIRIS images has so far not been able to confirm the little lander’s final location.

Philae’s descent to the surface, the initial touchdown at Agilkia at 15:34 UT (onboard spacecraft time) and first rebound were well-documented with the OSIRIS narrow-angle camera. The team also identified what they believe to be the lander in a wide-angle shot taken at 17:18 UT above the rim of the large depression – named Hatmehit – on the comet’s small lobe. The image has been used to guide subsequent lander search efforts, and provides the basis for trajectory reconstructions. According to data recorded by Philae’s ROMAP instrument, the lander may have grazed the surface at 16:20 UT – so this image may have captured the result of that encounter.

Philae_above_the_comet_node_full_image_2[1]Philae above the comet?
Rosetta’s OSIRIS wide-angle camera captured this view of
Comet 67P/Churyumov–Gerasimenko on 12 November 2014
at 17:18 GMT (onboard spacecraft time). Marked is what the OSIRIS
team believe to be the Philae lander above the rim of the large
depression – named Hatmehit – on the comet’s small lobe. The
image has been used to guide subsequent lander search efforts,
and provides the basis for trajectory reconstructions.
Credits: ESA/Rosetta/MPS for OSIRIS Team

Philae’s onboard data subsequently recorded the next touchdown at 17:25 UT and its final touchdown at 17:32 UT, at a site that has now been named “Abydos” (the first touchdown site remains as Agilkia). Images sent back by the CIVA imager onboard the lander and subsequent reconstructions are providing clues as to the nature of the landing site, but a visual confirmation is still required to confirm its location.

Follow-up dedicated OSIRIS imaging campaigns that took place in late November and December from distances of 30 and 20 km from the centre of the comet (about 28 and 18 km from the surface, respectively) have not been successful in locating the lander. The campaigns specifically targeted the times that the lander would be illuminated – it is illuminated approximately 1.3 hours per comet revolution – and that Rosetta had the correct orbital position to be able to image it. However, the cameras were looking into long cast shadows from Rosetta’s terminator orbit, perpendicular to the Sun direction, which does not provide the optimum conditions for detecting the lander.

It is also important to note that Rosetta’s trajectory immediately following Philae’s touchdown allowed for good viewing conditions at the original landing site. Now that Rosetta has moved to a different orbit, and is further away from the comet, the chances of observing the lander are less (watch this video for a recap of the different trajectories following the landing).

The image below is an example of the images being used to search for the lander; it is a slightly cropped 2 x 2 mosaic taken by the OSIRIS narrow-angle camera on 13 December 2014 from a distance of about 20 km to the centre of the comet. For the 20 km imaging run 18 sets of two images were taken – one each with orange and blue filters to take advantage of the reflection of the lander solar panels, which differ compared to the cometary environment. The images were taken in the 2 x 2 rasters to ensure good surface coverage. The lander, about 1 metre across – the size of a household washing machine – would measure only about three pixels across in these images.

Lander_search_area_node_full_image_2[1]Lander search area
An example of the OSIRIS narrow-angle camera mosaics being used to search
for Rosetta’s lander, Philae. The image is a slightly cropped 2 x 2 mosaic
comprising images taken on 13 December 2014 from a distance of about
20 km to the centre of the comet. The lander, about 1 m across –
the size of a household washing machine – would measure only about
three pixels across in these images. The team are searching – by eye – for a
set of three spots that correspond to the lander shape, but with the region
strewn with boulders it is soon easy to identify multiple sets of three spots.
Credits: ESA/Rosetta/MPS for OSIRIS Team

“We’re looking – by eye – for a set of three spots that correspond to the lander,” says OSIRIS principal investigator Holger Sierks from the Max Planck Institute for Solar System Research (MPS) in Germany. “The problem is that sets of three spots are very common all over the comet nucleus; Hatmehit and the area around its rim where we’re looking is full of boulders and we have identified several sets of three spots.”

Although Rosetta is flying to within 6 km of the comet’s surface on 14 February, the planned trajectory foresees the closest approach on the lower part of the larger comet lobe (although the trajectory also takes Rosetta over the first touchdown point). This trajectory is planned such that the Sun will be directly behind the spacecraft, allowing the acquisition of shadow-free images. The close flyby will also allow the suite of science instruments on the orbiter to take spectra of the surface with unprecedented resolution and to directly sample the very innermost regions of the cometary coma in order to learn more about how the comet’s characteristic coma and tail develop.

“Rosetta’s busy science schedule is planned several months in advance, so a dedicated Philae search campaign was not built into the plan for the close flyby,” says ESA’s Rosetta project scientist Matt Taylor. “We’ll be focusing on “co-riding” observations from now on, that is, we won’t be changing the trajectory of Rosetta to specifically fly over the predicted landing zone in a dedicated search, but we can modify the spacecraft pointing and/or command images to be taken of the region if we’re flying close to the region and the science operations timeline allows.”

“After the flyby we’ll be much further away from the comet again, so are unlikely to have the opportunity for another dedicated lander search until later in the mission, maybe even next year,” adds ESA’s Rosetta mission manager Fred Jansen. “But the location of Philae is not required to be able to operate it, and neither does it need to be awake for us to find it.”

When will Philae wake up?

For those of you who followed the wake-up of Rosetta, you will know that it is not simply a case of switch on and get back to the science right away. The same goes for Philae.

Philae_orientation_visualisation_node_full_image_2[1]Philae orientation visualisation
The likely orientation of Rosetta’s lander, Philae, in a visualisation
of a topographic model of the comet’s surface.

At the original landing site, Philae was expected to receive around 6.5 hours of illumination per 12.4 hour comet day, with temperatures becoming too high by March 2015 to enable continued operations. Now, at its new location, the illumination is just 1.3 hours.

“Now we need the extra solar illumination provided by the comet’s closer proximity to the Sun by that time in order to bring the lander back to life,” says DLR’s Lander Project Manager Stephan Ulamec.

In fact, even by May, the Sun inclination will be such that it will be directly overhead of the predicted landing zone, although the lander’s orientation is such that it won’t be able to make full use of the maximum illumination on offer.

As for the process of wake up, and assuming Philae survived the low temperatures in its new residence, the earliest that the lander team expect it to be warm enough to boot up is in late March. But it will likely be May or June before there is enough solar illumination to use its transmitter, and to re-establish a communications link with Rosetta – the lander needs about 17 Watts to wake up and say “hello”.

Furthermore, the orbiter also has to be commanded to listen for Philae’s “I’m awake” signal, and be in a good position relative to the landing site to pick up the signal – although it can be up to 200 km away from the comet. It will be longer still before the battery is fully charged and Philae is ready to do science again, but that means there is a chance it will have a ringside seat for perihelion.

“We are already discussing and preparing which instruments should be operated for how long,” adds Stephan.

But even if Philae doesn’t wake up, it’s important to remember that it already completed its first science sequence on the comet, unexpectedly providing information from multiple locations on 67P/C-G.

Meanwhile Rosetta will continue to follow the comet on its orbit around the Sun and as it heads back towards the outer Solar System.

Asteroids & Comets, Space Science

Dawn returns best-ever images of dwarf planet Ceres

The Dawn spacecraft moves closer to the dwarf planet Ceres in the asteroid belt (compare to a week ago).

NASA’s Dawn Spacecraft Captures Best-Ever View of Dwarf Planet

January 27, 2015—NASA’s Dawn spacecraft has returned the sharpest images ever seen of the dwarf planet Ceres. The images were taken 147,000 miles (237,000 kilometers) from Ceres on Jan. 25, and represent a new milestone for a spacecraft that soon will become the first human-made probe to visit a dwarf planet.

Ceres_OpNav2_Anim_v2[1]Ceres Sharper Than Ever Animation

This animation of the dwarf planet Ceres was made by combining images taken by NASA’s Dawn spacecraft on January 25, 2015. The spacecraft’s framing camera took these images, at a distance of about 147,000 miles (237,000 kilometers) from Ceres, and they represent the highest-resolution views to date of the dwarf planet. 

“We know so little about our vast solar system, but thanks to economical missions like Dawn, those mysteries are being solved,” said Jim Green, Planetary Science Division Director at NASA Headquarters in Washington.

At 43 pixels wide, the new images are more than 30 percent higher in resolution than those taken by NASA’s Hubble Space Telescope in 2003 and 2004 at a distance of over 150 million miles (about 241 million kilometers). The resolution is higher because Dawn is traveling through the solar system to Ceres, while Hubble remains fixed in Earth orbit. The new Dawn images come on the heels of initial navigation images taken Jan. 13 that reveal a white spot on the dwarf planet and the suggestion of craters. Hubble images also had glimpsed a white spot on the dwarf planet, but its nature is still unknown.

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The white dot in the upper left is not yet identified. The image
was taken 147,000 miles (237,000 kilometers) from Ceres on
January 25, 2015 by NASA’s Dawn spacecraft.
Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA  

“Ceres is a ‘planet’ that you’ve probably never heard of,” said Robert Mase, Dawn project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We’re excited to learn all about it with Dawn and share our discoveries with the world.”

As the spacecraft gets closer to Ceres, its camera will return even better images. On March 6, Dawn will enter into orbit around Ceres to capture detailed images and measure variations in light reflected from Ceres, which should reveal the planet’s surface composition.

“We are already seeing areas and details on Ceres popping out that had not been seen before. For instance, there are several dark features in the southern hemisphere that might be craters within a region that is darker overall,” said Carol Raymond, deputy principal investigator of the Dawn mission at JPL. “Data from this mission will revolutionize our understanding of this unique body. Ceres is showing us tantalizing features that are whetting our appetite for the detailed exploration to come.”

Ceres, the largest body between Mars and Jupiter in the main asteroid belt, has a diameter of about 590 miles (950 kilometers). Some scientists believe the dwarf planet harbored a subsurface ocean in the past and liquid water may still be lurking under its icy mantle.

Originally described as a planet, Ceres was later categorized as an asteroid, and then reclassified as a dwarf planet in 2006. The mysterious world was discovered in 1801 by astronomer Giuseppe Piazzi, who named the object for the Roman goddess of agriculture, grain crops, fertility and motherly relationships.

“You may not realize that the word ‘cereal’ comes from the name Ceres. Perhaps you already connected with the dwarf planet at breakfast today,” said JPL’s Marc Rayman, mission director and chief engineer of the Dawn mission.

Powered by a uniquely capable ion propulsion system, Dawn also orbited and explored Vesta, the second most massive body in the asteroid belt. From 2011 to 2012, Dawn returned more than 30,000 images, 18 million light measurements and other scientific data about the impressive large asteroid. Vesta has a diameter of about 326 miles (525 kilometers).

“With the help of Dawn and other missions, we are continually adding to our understanding of how the solar system began and how the planets were formed,” said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles.

Dawn’s mission to Vesta and Ceres is managed by JPL for NASA’s Science Mission Directorate in Washington. Dawn is a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. of Dulles, Virginia, designed and built the spacecraft. JPL is managed for NASA by the California Institute of Technology in Pasadena.

The framing cameras were provided by the Max Planck Institute for Solar System Research in Gottingen, Germany, with significant contributions by the German Aerospace Center (DLR) Institute of Planetary Research in Berlin, and in coordination with the Institute of Computer and Communication Network Engineering in Braunschweig.

The visible and infrared mapping spectrometer was provided by the Italian Space Agency and the Italian National Institute for Astrophysics, was built by Selex ES, and is managed by Italy’s National Institute for Astrophysics and Planetology in Rome. The gamma ray and neutron detector was built by Los Alamos National Laboratory in New Mexico, and is operated by the Planetary Science Institute of Tucson, Arizona.

The new Dawn images are available online at:  go.nasa.gov/1wyp0LA

To view the images taken by Hubble, visit: go.nasa.gov/1Ju41mf

Asteroids & Comets, Space Science

Video: Seminar on the Rosetta Lander (Philae) mission to comet 67P/C-G

Here’s a SETI Institute seminar by Jens Biele of the German space agency (DLR) in which he talks about the ESA Rosetta/Philae landing on Comet 67P/C-G: The Rosetta Lander (PHILAE) mission: landing on comet 67P/Churyumov-Gerasimenko – SETI Institute

Here is the caption to the video:

The Rosetta Lander (PHILAE) mission: landing on comet 67P/Churyumov-Gerasimenko

The Rosetta Lander, Philae, landed on 67P/Churyumov Gerasimenko on 12 November 2014. Before this could happen, a landing site had to be selected within just 2 months, based on data from the Rosetta Orbiter instruments and analyses on flight dynamics and illumination profiles. Philae was programmed to perform a First Scientific Sequence, immediately following touch down, and then enter its long term science mode.

The paper will report on the actual landing and the very first results. The landing was successful, though the operational sequences had to be modified ad hoc: Philae did not anchor upon first touchdown at 15:34:06 UTC but rebounded at least once, finally settling – fully operating all the while – at a place not ideal for long-term science. A wealth of science data has been received.

Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta’s Philae lander is provided by a consortium led by DLR, MPS, CNES and ASI.