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

Dawn Journal | May 31

by Marc Rayman
 

Dear Dawnosaurs,

Silently streaking through the main asteroid belt, emitting a blue-green beam of xenon ions, Dawn continues its ambitious interplanetary expedition. On behalf of creatures on distant Earth who seek not only knowledge and insight but also bold adventure, the spacecraft is heading toward its appointment with Ceres. In about 10 months, it will enter orbit around the ancient survivor from the dawn of the solar system, providing humankind with its first detailed view of a dwarf planet.

This month we continue with the preview of how Dawn will explore Ceres. In December we focused on the “approach phase,” and in January we described how the craft spirals gracefully into orbit with its extraordinary ion propulsion system. The plans for the first observational orbit (with a marvelously evocative name for a first examination of an uncharted world: RC3 — is that cool, or what?), at an altitude of 8,400 miles (13,500 kilometers), were presented in FebruaryLast month, we followed Dawn on its spiral descent from each orbital altitude to the next, with progressively lower orbits providing better views than the ones before. Now we can look ahead to the second orbital phase, survey orbit.

Survey_orbit

This figure shows Dawn’s second observational orbit, “survey orbit,” at the same scale as the size of Ceres. At an altitude of 2,730 miles (4,400 kilometers), the spacecraft will make seven revolutions in about three weeks. Credit: NASA/JPL

In survey orbit, Dawn will make seven revolutions at an altitude of about 2,730 miles (4,400 kilometers). At that distance, each orbit will take three days and three hours. Mission planners chose an orbit period close to what they used for survey orbit at Vesta, allowing them to take advantage of many of the patterns in the complex choreography they had already developed. Dawn performed it so beautifully that it provides an excellent basis for the Ceres encore. Of course, there are some adjustments, mostly in the interest of husbanding precious hydrazine propellant in the wake of the loss of two of the spacecraft’s four reaction wheels. (Although such a loss could have dire consequences for some missions, the resourceful Dawn team has devised a plan that can achieve all of the original objectives regardless of the condition of the reaction wheels.)

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29 May
2014

Greetings From Berlin–Grüße aus Berlin!

by Chris Russell
 

The Dawn Team Converges at the German Aerospace Agency

The Dawn spacecraft moved back in solar system time when it cruised into the main asteroid belt, first orbiting protoplanet Vesta in 2011-12, and now on its way to dwarf planet Ceres, due in March 2015. When the Dawn team met in Berlin this month, it offered an opportunity for the mission to do a bit of its own time travel.

Dawn Team at the German Aerospace Agency, Berlin, 2014

fig 1: Dawn Team at the German Aerospace Agency, Berlin, 2014

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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.

 

2 May
2014
Marc Rayman
Marc Rayman
Chief Engineer/ Mission Director, JPL

The Hundredth Journal

by Marc Rayman
 
Colleague Keri Bean's festive (and delicious) cake

Colleague Keri Bean’s festive (and delicious) cake with some of the greetings used in the Dawn Journals.

I have been captivated by space since I was four years old, and my enthusiasm has grown stronger and stronger ever since. With a lifelong passion for the exploration and utilization of space, covering the science, the engineering and the pure thrill of a cosmic adventure, working on a mission to explore some of the last uncharted worlds in the inner solar system has been a dream come true for me. My work is indescribably exciting.

And although it literally is indescribable, I can’t help but try! As one facet of that effort, I started writing the Dawn Journal eight years ago. Now that I have written 100, I was invited to write a short blog to celebrate. (In other words, I’ve been asked to blog about blogging.)

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

Dawn Journal | April 30

by Marc Rayman
 

Dear Compedawnt Readers,

Less than a year from its rendezvous with dwarf planet Ceres, Dawn is continuing to make excellent progress on its ambitious interplanetary adventure. The only vessel from Earth ever to take up residence in the main asteroid belt between Mars and Jupiter, the spacecraft grows more distant from Earth and from the sun as it gradually closes in on Ceres. Dawn devotes the majority of its time to thrusting with its remarkable ion propulsion system, reshaping its heliocentric path so that by the time it nears Ceres, the explorer and the alien world will be in essentially the same orbit around the sun.

Dawn thrusting in orbit

Dawn will use its ion propulsion system to change orbits at Ceres, allowing it to observe the dwarf planet from different vantage points. Image credit: NASA/JPL

In December, we saw what Dawn will do during the “approach phase” to Ceres early in 2015, and in January, we reviewed the unique and graceful method of spiraling into orbit. We described in February the first orbit (with the incredibly cool name RC3) from which intensive scientific observations will be conducted, at an altitude of 8,400 miles (13,500 kilometers). But Dawn will take advantage of the extraordinary capability of ion propulsion to fly to three other orbital locations from which it will further scrutinize the mysterious world.

Let’s recall how the spacecraft will travel from one orbit to another. While some of these plans may sound like just neat ideas, they are much more than that; they have been proven with outstanding success. Dawn maneuvered extensively during its 14 months in orbit around Vesta. (One of the many discussions of that was in November 2011.) The seasoned space traveler and its veteran crew on distant Earth are looking forward to applying their expertise at Ceres.

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

Dawn Journal | March 31

by Marc Rayman
 

Dear Correspondawnts,

Powering its way through deep space, Dawn draws ever closer to dwarf planet Ceres. To reach its destination, the interplanetary spaceship gently reshapes its path around the sun with its extraordinary ion propulsion system. In about a year, the spacecraft will gracefully slip into orbit so it can begin to unveil the nature of the mysterious world of rock and ice, an intriguing protoplanetary remnant from the dawn of the solar system.

Even as Dawn ascends the solar system hill, climbing farther and farther from the sun, penetrating deeper into the main asteroid belt between Mars and Jupiter, its distance to Earth is shrinking. This behavior may be perplexing for readers with a geocentric bias, but to understand it, we can take a broader perspective.

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21 Mar
2014

Space Inspired “Nerd Couture”

by Dawn EPO
 
Two Dawn engineers showing off their nail art

Dawn mission-inspired nail art matches the spacecraft’s solar panels.

Dawn Rocks the Community

Two members of the Dawn mission have taken space exploration to a new level, combining space—and fashion. Meet Keri Bean and Kristina Larson. Keri is a member of Dawn’s science operations team and Kristina works for the spacecraft flight team at NASA’s Jet Propulsion Laboratory.  Their shared interest in “nerd couture” brought them together, as well as their obsession with space nail art. They like wearing fashionable clothing that also expresses their interests in space science and other “nerdy” topics. From space shuttle shoes to Dawn-inspired solar panel nails, they wear it all!

Keri Bean Dawn mission science operations, and Kristina Larson, Dawn spacecraft flight team

Keri Bean, Dawn mission science operations, and Kristina Larson, Dawn spacecraft flight team, sporting “nerd couture”

In her role in science planning and sequencing, Keri acts as the interface between different off-site science team members and the spacecraft operations team at JPL.  While an undergrad and grad student at Texas A&M University, Keri was on science teams for multiple Mars missions and now uses those skills in exploring the two largest bodies in the asteroid belt.

Kristina does similar work as part of the engineering operations team by planning and sequencing engineering activities, as well as sending commands to the spacecraft and testing them on the testbed.  She has interned on Dawn since her sophomore year at USC, where she got her undergrad and grad degrees in Aerospace Engineering. Kristina worked previously on a Mars rover as a Tactical Downlink Lead, planning activities for the rover and analyzing downlinked data.

Keri Bean and her space dress, accented by her Dawn Lego model!

Keri Bean and her space dress, accented by her Dawn Lego model!

They hope to continue to share their unique and quirky styles as well as glam ideas through the eyes of two young women and hopefully teach you about Dawn along the way—so stay tuned!


 

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

Dawn Journal | February 28, 2014

by Marc Rayman
 

Dear Ardawnt Readers,

Continuing its daring mission to explore some of the last uncharted worlds in the inner solar system, Dawn remains on course and on schedule for its rendezvous with dwarf planet Ceres next year. Silently and patiently streaking through the main asteroid belt between Mars and Jupiter, the ardent adventurer is gradually reshaping its orbit around the sun with its uniquely efficient ion propulsion system. Vesta, the giant protoplanet it unveiled during its spectacular expedition there in 2011-2012, grows ever more distant.

Dawn will  uses ion propulsion system to spiral to RC3 orbit

Following its gravitational capture by Ceres during the approach phase, Dawn will continue to use its ion propulsion system to spiral to RC3 orbit at an altitude of 8,400 miles (13,500 kilometers). Credit: JPL/NASA

In December and January, we saw Dawn’s plans for the “approach phase” to Ceres and how it will slip gracefully into orbit under the gentle control of its ion engine. Entering orbit, gratifying and historic though it will be, is only a means to an end. The reason for orbiting its destinations is to have all the time needed to use its suite of sophisticated sensors to scrutinize these alien worlds.

As at Vesta, Dawn will take advantage of the extraordinary capability of its ion propulsion system to maneuver extensively in orbit at Ceres. During the course of its long mission there, it will fly to four successively lower orbital altitudes, each chosen to optimize certain investigations. (The probe occupied six different orbits at Vesta, where two of them followed the lowest altitude. As the spacecraft will not leave Ceres, there is no value in ascending from its fourth and lowest orbit.) All of the plans for exploring Ceres have been developed to discover as much as possible about this mysterious dwarf planet while husbanding the precious hydrazine propellant, ensuring that Dawn will complete its ambitious mission there regardless of the health of its reaction wheels.

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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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