Archive for the ‘Science’ Category

In 2014, the Dawn Mission Journal implemented a new blog that includes Dawn Journal entries posted from 2014 to the present. All entries can be accessed on the Dawn website.

Dawn Journal entries currently residing on the Dawn blog can be viewed by selecting Dawn Journal under the Categories Section on the top right-hand side of every post.


 

28 Nov
2014
Marc Rayman
Marc Rayman
Chief Engineer/ Mission Director, JPL

Dawn Journal | November 28

by Marc Rayman
 

Dear Unidawntified Flying Objects,

Flying silently and smoothly through the main asteroid belt between Mars and Jupiter, Dawn emits a blue-green beam of high velocity xenon ions. On the opposite side of the sun from Earth, firing its uniquely efficient ion propulsion system, the distant adventurer is continuing to make good progress on its long trek from the giant protoplanet Vesta to dwarf planet Ceres.

This month, let’s look ahead to some upcoming activities. You can use the sun in December to locate Dawn in the sky, but before we describe that, let’s see how Dawn is looking ahead to Ceres, with plans to take pictures on the night of Dec. 1.

The robotic explorer’s sensors are complex devices that perform many sensitive measurements. To ensure they yield the best possible scientific data, their health must be carefully monitored and maintained, and they must be accurately calibrated. The sophisticated instruments are activated and tested occasionally, and all remain in excellent condition. One final calibration of the science camera is needed before arrival at Ceres. To accomplish it, the camera needs to take pictures of a target that appears just a few pixels across. The endless sky that surrounds our interplanetary traveler is full of stars, but those beautiful pinpoints of light, while easily detectable, are too small for this specialized measurement. But there is an object that just happens to be the right size. On Dec. 1, Ceres will be about nine pixels in diameter, nearly perfect for this calibration.

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17 Nov
2014

Dawn Soars at 2014 JPL Open House

by Dawn Education & Communications
 

Two days…
…200+ scientists and engineers…
…Live demonstrations…
…NASA’s thrilling space science.

What happens when people come together with a common mission to tell the stories of NASA and make it happen? 45,716 visitors traveled from afar to find out at the 2014 JPL Open House in Pasadena, California on October 11-12. The event, themed “Welcome to Our Universe,” invited visitors on a “ride” through the wonders of space. Highlights included a life-size model of the Curiosity rover and demonstrations from numerous space missions—including Dawn. Dawn visited giant asteroid Vesta from 2011 to 2012, and will arrive at dwarf planet Ceres in the spring of 2015. A 3-D print of protoplanet Vesta, gorgeous images, and an ion engine just like the one being used by Dawn to orbit its destinations helped the mission’s scientists and engineers tell the tale of the science, technology, engineering and mathematics (STEM) that drives the mission!

JPL Open house

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31 Oct
2014
Marc Rayman
Marc Rayman
Chief Engineer/ Mission Director, JPL

Dawn Journal | October 31

by Marc Rayman
 

Dear Dawnomalies,

Farther from Earth and from the sun than it has ever been, Dawn is on course and on schedule for its March 2015 arrival at Ceres, an enigmatic world of rock and ice. To slip gracefully into orbit around the dwarf planet, the spacecraft has been using its uniquely capable ion propulsion system to reshape its heliocentric orbit so that it matches Ceres’ orbit. Since departing the giant protoplanet Vesta in Sep. 2012, the stalwart ship has accomplished 99.46 percent of the planned ion thrusting.

What matters most for this daring mission is its ambitious exploration of two uncharted worlds (previews  of the Ceres plan were presented from December 2013 to August 2014), but this month and next, we will consider that 0.54 percent of the thrusting Dawn did not accomplish. We begin by seeing what happened on the spacecraft and in mission control. In November we will describe the implications for the approach phase of the mission. (To skip now to some highlights of the new approach schedule, click on the word “click.”)

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21 Oct
2014

In Appreciation: Dr. Gerhard Neukum

by Dawn Education & Communications
 
Dr. Gerhard Neukum

Professor of Planetary
Sciences, Freie Universität Berlin. Credit: ESA

We are remembering Gerhard Neukum today: a mentor, a friend, and a superlative colleague.

Professor Gerhard Neukum was a planetary scientist with a particular fascination for craters and the story they tell about the age and composition of a solar system body—and the solar system itself. A co-investigator on the Dawn science team, he advised with characteristic perception and tenacity.

DoubleCrater_Mar2012

Gerhard Neukum was an international expert on cratering. Double crater on giant asteroid Vesta.
Credit: NASA/ JPL-Caltech/ UCLA/ MPS/ DLR/ IDA

Neukum’s career as a distinguished planetary scientist began in the 1970s, when he conducted research for NASA’s Apollo program as a physics student at the University of Heidelberg. Eventually he became the director of the German Aerospace Center Institute of Planetary Research before moving to the Free University of Berlin. Throughout his long and successful career he made major contributions to international space missions that visited the moon, Mars, Jupiter, Saturn, and the main asteroid belt. Neukum will always be remembered for his uncompromising determination to explore the solar system. Without his charismatic leadership, planetary science would not be where it is today.

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27 Sep
2014
Marc Rayman
Marc Rayman
Chief Engineer/ Mission Director, JPL

Dawn Journal | September 27

by Marc Rayman
 

Dear Dawnniversaries,

On the seventh anniversary of embarking upon its extraordinary extraterrestrial expedition, the Dawn spacecraft is far from the planet where its journey began. While Earth has completed its repetitive loops around the sun seven times, its ambassador to the cosmos has had a much more varied itinerary. On most of its anniversaries, including this one, it reshapes its orbit around the sun, aiming for some of the last uncharted worlds in the inner solar system. (It also zipped past the oft-visited Mars, robbing the red planet of some of its orbital energy to help fling the spacecraft on to the more distant main asteroid belt.) It spent its fourth anniversary exploring the giant protoplanet Vesta, the second most massive object in the asteroid belt, revealing a fascinating, complex, alien place more akin to Earth and the other terrestrial planets than to typical asteroids. This anniversary is the last it will spend sailing on the celestial seas. By its eighth, it will be at its new, permanent home, dwarf planet Ceres.

The mysterious world of rock and ice is the first dwarf planet discovered (129 years before Pluto) and the largest body between the sun and Pluto that a spacecraft has not yet visited. Dawn will take up residence there so it can conduct a detailed investigation, recording pictures and other data not only for scientists but for everyone who has ever gazed up at the night sky in wonder, everyone who is curious about the nature of the universe, everyone who feels the burning passion for adventure and the insatiable hunger for knowledge and everyone who longs to know the cosmos.

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31 Aug
2014
Marc Rayman
Marc Rayman
Chief Engineer/ Mission Director, JPL

Dawn Journal | August 31

by Marc Rayman
 

Dear Omnipodawnt Readers,

Dawn draws ever closer to the mysterious Ceres, the largest body between the sun and Pluto not yet visited by a probe from Earth. The spacecraft is continuing to climb outward from the sun atop a blue-green beam of xenon ions from its uniquely efficient ion propulsion system. The constant, gentle thrust is reshaping its solar orbit so that by March 2015, it will arrive at the first dwarf planet ever discovered. Once in orbit, it will undertake an ambitious exploration of the exotic world of ice and rock that has been glimpsed only from afar for more than two centuries.

An important characteristic of this interplanetary expedition is that Dawn can linger at its destinations, conducting extensive observations. Since December, we have presented overviews of all the phases of the mission at Ceres save one. (In addition, questions posted by readers each month, occasionally combined with an answer, have helped elucidate some of the interesting features of the mission.) We have described how Dawn will approach its gargantuan new home (with an equatorial diameter of more than 600 miles, or 975 kilometers) and slip into orbit with the elegance of a celestial dancer. The spacecraft will unveil the previously unseen sights with its suite of sophisticated sensors from progressively lower altitude orbits, starting at 8,400 miles (13,500 kilometers), then from survey orbit at 2,730 miles (4,400 kilometers), and then from the misleadingly named high altitude mapping orbit (HAMO) only 910 miles (1,470 kilometers) away. To travel from one orbit to another, it will use its extraordinary ion propulsion system to spiral lower and lower and lower. This month, we look at the final phase of the long mission, as Dawn dives down to the low altitude mapping orbit (LAMO) at 230 miles (375 kilometers). We will also consider what future awaits our intrepid adventurer after it has accomplished the daring plans at Ceres.

From HAMO to LAMO

Dawn’s spiral transfer from HAMO to LAMO. The trajectory turns from blue to red as time progresses during the two months. Red dashed sections are where ion thrusting is stopped so the spacecraft can point its main antenna to Earth. Credit: NASA/JPL

It will take the patient and tireless robot two months to descend from HAMO to LAMO, winding in tighter and tighter loops as it goes. By the time it has completed the 160 revolutions needed to reach LAMO, Dawn will be circling Ceres every 5.5 hours. (Ceres rotates on its own axis in 9.1 hours.) The spacecraft will be so close that Ceres will appear as large as a soccer ball seen from 3.5 inches (less than nine centimeters) away. In contrast, Earth will be so remote that the dwarf planet would look to terrestrial observers no larger than a soccer ball from as far as 170 miles (270 kilometers). Dawn will have a uniquely fabulous view.

As in the higher orbits, Dawn will scrutinize Ceres with all of its scientific instruments, returning pictures and other information to eager Earthlings. The camera and visible and infrared mapping spectrometer (VIR) will reveal greater detail than ever on the appearance and the mineralogical composition of the strange landscape. Indeed, the photos will be four times sharper than those from HAMO (and well over 800 times better than the best we have now from Hubble Space Telescope). But just as in LAMO at Vesta, the priority will be on three other sets of measurements which probe even beneath the surface.

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31 Jul
2014
Marc Rayman
Marc Rayman
Chief Engineer/ Mission Director, JPL

Dawn Journal | July 31

by Marc Rayman
 

Dear Studawnts and Teachers,

Patient and persistent, silent and alone, Dawn is continuing its extraordinary extraterrestrial expedition. Flying through the main asteroid belt between Mars and Jupiter, the spacecraft is using its advanced ion propulsion system to travel from Vesta, the giant protoplanet it unveiled in 2011 and 2012, to Ceres, the dwarf planet it will reach in about eight months.

Most of these logs since December have presented previews of the ambitious plan for entering orbit and operating at Ceres to discover the secrets this alien world has held since the dawn of the solar system. We will continue with the previews next month. But now with Dawn three quarters of the way from Vesta to Ceres, let’s check in on the progress of the mission, both on the spacecraft and in mission control at JPL.

The mission is going extremely well. Thank you for asking.

For readers who want more details, read on…

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30 Jun
2014
Marc Rayman
Marc Rayman
Chief Engineer/ Mission Director, JPL

Dawn Journal | June 30

by Marc Rayman
 

Dear Mastodawns,

Deep in the main asteroid belt, between Mars and Jupiter, far from Earth, far from the the sun, far now even from the giant protoplanet Vesta that it orbited for 14 months, Dawn flies with its sights set on dwarf planet Ceres. Using the uniquely efficient, whisper-like thrust of its remarkable ion propulsion system, the interplanetary adventurer is making good progress toward its rendezvous with the uncharted, alien world in about nine months.

Dawn’s ambitious mission of exploration will require it to carry out a complex plan at Ceres. In December, we had a preview of the “approach phase,” and in January, we saw how the high velocity beam of xenon ions will let the ship slip smoothly into Ceres’s gravitational embrace. We followed that with a description in February of the first of four orbital phases (with the delightfully irreverent name RC3), in which the probe will scrutinize the exotic landscape from an altitude of 8,400 miles (13,500 kilometers). We saw in April how the spacecraft will take advantage of the extraordinary maneuverability of ion propulsion to spiral from one observation orbit to another, each one lower than the one before, and each one affording a more detailed view of the exotic world of rock and ice. The second orbit, at an altitude of about 2,730 miles (4,400 kilometers), known to insiders (like you, faithful reader) as “survey orbit,” was the topic of our preview in May. This month, we will have an overview of the plan for the third and penultimate orbital phase, the “high altitude mapping orbit” (HAMO).

(The origins of the names of the phases are based on ancient ideas, and the reasons are, or should be, lost in the mists of time. Readers should avoid trying to infer anything at all meaningful in the designations. After some careful consideration, your correspondent chose to use the same names the Dawn team uses rather than create more helpful descriptors for the purposes of these logs. What is important is not what the different orbits are called but rather what amazing new discoveries each one enables.)

It will take Dawn almost six weeks to descend to HAMO, where it will be 910 miles (1,470 kilometers) high, or three times closer to the mysterious surface than in survey orbit. As we have seen before, a lower orbit, whether around Ceres, Earth, the sun, or the Milky Way galaxy, means greater orbital velocity to balance the stronger gravitational grip. In HAMO, the spacecraft will complete each loop around Ceres in 19 hours, only one quarter of the time it will take in survey orbit.

Sprial to Hamo

Dawn’s spiral descent from survey orbit to the high altitude mapping orbit. The trajectory progresses from blue to red over the course of the six weeks. The red dashed segments are where the spacecraft is not thrusting with its ion propulsion system (as explained in April). Credit: NASA/JPL

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23 May
2014

Vesta 360

by David O'Brien
 

The Dawn mission is currently en route to dwarf planet Ceres, its second destination. It spent a productive fourteen months orbiting its first destination, giant asteroid Vesta, in 2011-12, gathering splendid sets of data. The spacecraft may have moved on, but the science team continues to explore that data, enriching our understanding of Vesta’s formation and history.

Getting the “Big Picture”

Vesta: Clementine color ratios

Clementine color ratios

Vesta is a large protoplanet with remarkably variable topography—mountains, troughs, boulders, craters, cliffs, and more. The wealth of high-resolution imaging data from the Dawn mission has given us an amazing view of its surface. However, looking through individual frames or image mosaics can make it difficult to see its surface features in a global context and get the “big picture” of Vesta. On the other hand, the images taken early on as the mission approached the protoplanet show the whole of Vesta, but with low surface resolution. To better visualize Vesta at high resolution, I used the open-source program POV-Ray[1], combining images and topography data to create striking 3-D graphics.

The program let me take a shape model of Vesta, created from Dawn’s framing camera data by Bob Gaskell at the Planetary Science Institute, and wrap an image around it. For the image, I used a global mosaic[2] developed by our framing camera team partners at the German Aerospace Center (DLR) from high altitude mapping orbit clear-filter images. This mosaic has a resolution of 60 meters (about 200 feet) per pixel. I then used POV-Ray to make ‘snapshots’ of this model of Vesta as it rotated, varying the latitude from +45 to -45 degrees. Those individual frames were combined into the movie shown below.

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Footnotes:
  1. [1] Persistence of Vision Raytracer
  2. [2] The global mosaics used here can be downloaded from this page at the Dawn Public Data website, although they are very large files. For labeled maps of smaller regions of the surface, see the Vesta Atlas.


 

25 Feb
2014

Virtual Tour of Vesta

by Thomas Roatsch
 

The International Astronomical Union recently approved a new set of feature names for giant asteroid Vesta: Albia, Africana and Alypia Craters, to name a few. Among the features are dorsa (ridges), fossae (long, narrow shallow depressions), a rupes (scarp or cliff), and craters from Vesta’s mysterious north polar region. This compels us to take another close look at Vesta’s marvelous atlas.

An atlas of the asteroid Vesta, created from images taken during the Dawn mission’s low altitude mapping orbit (LAMO), is accessible for the public to explore online.  The set of maps was created from mosaics of 10,000 images from Dawn’s framing camera (FC) instrument, taken at an altitude of about 210 kilometers.  The maps are mostly at a scale of 1:200 0000 (1 centimeter = 2 kilometers), about that of regional road maps.

 Vesta's Low Altitude Mapping Orbit (LAMO) Atlas is at the scale of regional road maps: 1cm = 2 km (1 in = 3 mi).

Vesta’s Low Altitude Mapping Orbit (LAMO) Atlas is at the scale of regional road maps: 1 cm = 2 km (1 in = 3 mi)
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Creating the atlas was a painstaking task – each map sheet of this series used roughly 400 images. The atlas shows how extreme the terrain is on a body the size of Vesta.  In the south pole projection alone, the Severina crater contours reach a depth of 18 kilometers; just over a hundred kilometers away the mountain peak towers 7 kilometers above the ellipsoid reference level.

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