When you read my blog, you’re either going to say “no way” or “finally.” And honestly, I’m kind of saying both, but definitely leaning more toward the latter.

See, normally I’m weighed down by the epic crisis known as global climate change (ugh). But this morning, I’m thinking: "finally." At last, Earth’s climate is going to get the attention it deserves. Finally, enough people are showing they care and it’s going to make a difference. Finally.

True, it’s hard to believe—even for me. But deep in my bones, I feel the tide starting to turn. (And by using that expression, I do not mean higher tides are flooding low-lying regions. That’s been going on for a while.)

What I mean is that everywhere I turn I see people paying attention to Earth’s climate. Not enough attention yet, mind you, but at least people are talking about it. And for the first time in a long time, I feel hopeful.

Maybe this optimism has something to do with the rainbow I saw while walking out in the rain over the weekend. Maybe it’s because NASA’s Global Climate Change website won both the People’s Voice and the juried Webby Awards for Best Green Site, and our Earth Now mobile app won in the Education and Reference category.

Whatever it is, I hope you’ll join me in my moment of optimism, because together—you and me—we are responsible for making this planet the kind of world we want to live in.

Bring it.

- Laura

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Goldstone Antenna Construction Model

In October 1963, the Advanced Antenna System, also known as the 210-foot (64-meter) Mars antenna, was under construction at the Goldstone Deep Space Instrumentation Facility. The site was being cleared and a foundation dug, an access road was nearing completion, and a reservoir was built to provide water during construction. Assembly of the antenna required a 200-ton guy derrick, used to lift large pieces into place. In preparation for this stage of construction, scale models of the antenna and the guy derrick were built, showing how the derrick would be anchored to the desert floor by long cables.



  • Julie Cooper

Anaglyph of Ceres

Let's get Dawn to business, Dear Readers,




Illustration of Dawn’s four mapping orbits

















Dr. Marc D. Rayman
10:30 p.m. PDT April 29, 2015



  • Marc Rayman

Peas with an image of Earth

"Excuse me. What kind of plants are those?"

I was squatting down in my front yard as I do every morning, picking veggies for breakfast, when I heard a voice behind me. I stood up and turned around. It was a neighbor from across the street and three houses down. "They're peas," I told him.

A few years back, we were among the first in our neighborhood to rip out the grass in our parkway so we could plant drought-tolerant succulents and other cool-looking plants instead of boring, old, water-sucking grass. Little did I know that, along with saving money and water, the process also attracted the curiosity of lots of people on our street. We were bucking the trend, breaking the norm, doing something different. And people wanted to hear all about our new way-cooler-looking-than-grass plants.

Then we created a vegetable garden in the front yard. The goal was to have a cool modern-looking yard and have some fun growing and eating good food. We succeeded in harvesting enough kale, tomatoes, artichokes, chard and peas to feast on for many weeks (and I was able to include my own home-grown items in the yummy edible NASA satellite models I made).

But our gardening exploits brought us another unexpected advantage. We were already growing food in our backyard and side yard, but we learned that when you plant cool stuff in the front yard, lots of passersby stop to check it out. It's usually the artichokes that evoke the most frequent comments and questions. I mean, artichokes are weird-looking. (Shhh, don't you dare tell them I said that!) But over the years our vegetable garden has become a magnet that's attracted friendship and community in our neighborhood. And we've seen many other lawns turn into gardens, too.

There's no way to tell what will unfold when you start to do something, even the smallest thing. Actions grow and expand, sort of like the way our peas started out small, crawled past their trellises and are now getting tangled up into each other. What you create in the world can take on a life of its own, beyond what you might ever imagine.

Every Earth Day I write about taking an individual action, and every time I write this I get all kinds of criticism about how doing one small thing isn't enough.

But next time you start to think that your actions are too small to make a difference, think about me and my silly old peas. Remember that I reached down, picked a fresh pea and handed it across the stucco wall to the guy who lives down the street-the guy whom I hadn't yet connected with in all these years; one of the last of my neighbors to reach out. He told me that he and his wife saw our yard and decided to plant a garden as well.

And while you're at it, remember to celebrate Earth Day this year by joining NASA as we all share views of our favorite place on Earth on social media. We hope that if all of us take a moment to acknowledge and remember our planet, we'll feel more connected to it.

You can post photos, Vines and/or Instagram videos. Just be sure to include the hashtag #NoPlaceLikeHome - no matter what social media platform you're using.

You can also get on board now by using our #NoPlaceLikeHome emoji as your profile pic. Join the Facebook or Google+ events and invite your friends to participate. Pledge to spend one day celebrating the planet that over 7 billion people call home.

Find out more at

Thanks for everything you do to care for our planet.

I look forward to your comments.

- Laura

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A couple of weeks ago, I received an email from a high school student in Michigan. She was working on a climate change research project and wanted to ask me a few questions, so of course I said yes. She asked me about my job at NASA, what I thought were the most pressing aspects of Earth’s changing climate, and the ocean’s role in long-term climate trends.

But then there was this question: “I like to do everything I can each day to reduce my own contribution to climate change … I want to encourage my peers to take small actions each day to help our climate, but will it really matter beyond making people feel good about themselves? ... It seems like there is nothing individuals can do.”

Now I’m a pretty direct person, but I’m also fairly kind to high school students, especially those I’ve never even met. Yet this time, I let her have it:

“You are wrong,” I stated bluntly, wishing an error buzzer noise could accompany my outgoing email message. “You are wrong about your own contribution being insignificant. One person's efforts are hugely important and don't you ever forget it.”

Sure, I understand it’s easy to feel completely overwhelmed and powerless in the face of a tremendous problem such as climate change. I work on a climate change website every day—I get it. Just thinking about climate change and other environmental issues gets depressing. These problems are too big; they feel insurmountable. And then when you want to do something, it seems like whatever you do is too small, like a tiny drop in a gigantic pit.

But each and every single individual action, no matter how small it may seem, adds to what ultimately makes a difference. You may think, “One person isn’t going to make a big difference; it’s not going to be a big deal.” But taking responsibility for how your life affects the environment is a huge deal.

The Earth is amazing. And when you look at the view from space you see that the whole Earth is your home, our home. You see that what happens on the other side of the planet matters.

So go ahead: Take the journey from “there’s not much I can do” to “there are many things I will commit to doing.” Because together, our individual actions can make a bigger impact than you might ever imagine. And since Earth Day is coming up on April 22, now is the perfect time to begin that journey.

One of the things we’re doing to celebrate Earth Day this year is asking people around the world to share on social media views of their favorite place on Earth. As we rush through our busy lives, sometimes we forget to appreciate how much we care about this place we call home. We hope that if all of us take a moment to acknowledge and remember our planet, we'll feel more connected with it. And that's one small step toward making it a better place.

You can post photos, Vines and/or Instagram videos. Just be sure to include the hashtag #NoPlaceLikeHome – no matter what social media platform you’re using.


Find out more at

Thanks for everything you do to care for our planet.

- Laura

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one-tenth scale Cassegrain antenna feed system

In the early 1960s, a new large-aperture, low-noise Advanced Antenna System was in its planning and early development stages for the Deep Space Instrumentation Facility (later known as the Deep Space Network). Compared with the 85-ft (26-meter) antennas then in use, the new antenna was to give a 10-decibel performance increase, with an order of magnitude increase in the data rate from future spacecraft. Feasibility studies and testing were conducted by NASA's Jet Propulsion Laboratory in Pasadena, California, and subcontractors for various technologies and antenna components.

This January 1962 photo shows a 960-mc one-tenth scale Cassegrain antenna feed system study for the Advanced Antenna System. The objective was to establish the electrical performance capabilities and operational feasibility of this type of feed system for large antennas. The mount of the test system was covered with epoxy fiberglass and polystyrene foam to limit reflection of energy during testing.

A 210-foot (64-meter) antenna, using the new technology and designs, was built at the Goldstone site in California and became operational in 1966. The antenna, DSS 14, became known as the Mars antenna when it was used to track the Mariner 4 spacecraft. It was later upgraded to 70 meters in order to track Voyager 2 as it reached Neptune.



  • Julie Cooper

Image of dwarf planet Ceres from NASA's Dawn spacecraft

Dear Dawnticipating Explorers,

Now orbiting high over the night side of a dwarf planet far from Earth, Dawn arrived at its new permanent residence on March 6. Ceres welcomed the newcomer from Earth with a gentle but firm gravitational embrace. The goddess of agriculture will never release her companion. Indeed, Dawn will only get closer from now on. With the ace flying skills it has demonstrated many times on this ambitious deep-space trek, the interplanetary spaceship is using its ion propulsion system to maneuver into a circular orbit 8,400 miles (13,500 kilometers) above the cratered landscape of ice and rock. Once there, it will commence its first set of intensive observations of the alien world it has traveled for so long and so far to reach.


Among the many sights we eagerly anticipate are those captivating bright spots. Hinted at more than a decade ago by Hubble Space Telescope, Dawn started to bring them into sharper focus after an extraordinary journey of more than seven years and three billion miles (nearly five billion kilometers). Although the spots are reflections of sunlight, they seem almost to radiate from Ceres as cosmic beacons, drawing us forth, spellbound. Like interplanetary lighthouses, their brilliant glow illuminates the way for a bold ship from Earth sailing on the celestial seas to a mysterious, uncharted port. The entrancing lights fire our imagination and remind us of the irresistible lure of exploration and the powerful anticipation of an adventure into the unknown.

As we describe below, Dawn’s extensive photographic coverage of the sunlit terrain in early May will include these bright spots. They will not be in view, however, when Dawn spies the thin crescent of Ceres in its next optical navigation session, scheduled for April 10 (as always, all dates here are in the Pacific time zone).

As the table here shows, on April 14 (and extending into April 15), Dawn will obtain its last navigational fix before it finishes maneuvering. Should we look forward to catching sight of the bright spots then? In truth, we do not yet know. The spots surely will be there, but the uncertainty is exactly where “there” is. We still have much to learn about a dwarf planet that, until recently, was little more than a fuzzy patch of light among the glowing jewels of the night sky. (For example, only last month did we determine where Ceres’north and south poles point.) Astronomers had clocked the length of its day, the time it takes to turn once on its axis, at a few minutes more than nine hours. But the last time the spots were in view of Dawn’s camera was on Feb. 19. From then until April 14, while Earth rotates more than 54 times (at 24 hours per turn), Ceres will rotate more than 140 times, which provides plenty of time for a small discrepancy in the exact rate to build up. To illustrate this, if our knowledge of the length of a Cerean day were off by one minute (or less than 0.2 percent), that would translate into more than a quarter of a turn during this period, drastically shifting the location of the spots from Dawn’s point of view. So we are not certain exactly what range of longitudes will be within view in the scheduled OpNav 7 window. Regardless, the pictures will serve their intended purpose of helping navigators establish the probe’s location in relation to its gravitational captor.

Dawn’s gradual, graceful arc down to its first mapping orbit will take the craft from the night side to the day side over the north pole, and then it will travel south. It will conclude its powered flight over the sunlit terrain at about 60 degrees south latitude. The spacecraft will finish reshaping its orbit on April 23, and when it stops its ion engine on that date, it will be in its new circular orbit, designated RC3. (We will return to the confusing names of the different orbits at Ceres below.) Then it will coast, just as the moon coasts in orbit around Earth and Earth coasts around the sun. It will take Dawn just over 15 days to complete one revolution around Ceres at this height. We had a preview of RC3 last year, and now we can take an updated look at the plans.

OP NAV 5 image
Dawn’s final swoop down to RC3 orbit. The sun is off the figure far to the left, and Ceres’ north pole points up. The farther Dawn is to the right side of Ceres here, the smaller a crescent it sees, because the illumination is from the left. The white circles are at one-day intervals. The trajectory is solid where Dawn is thrusting with its ion engine, which is most of the time. The labels show four optical navigation sessions, where it pauses to turn, point at Ceres, conduct the indicated observation, turn to point its main antenna to Earth, transmit its findings, turn back to the orientation needed for thrusting, and then restart the ion engine. Dawn was captured into orbit on March 6. Note the periods on the right side of the figure between OpNav 5 (on March 1) and OpNav 6 (on April 10) when Dawn pauses thrusting for telecommunications and radio navigation but does not take pictures because it would have to point its instruments too close to the sun. Apodemeter is the Dawn team’s word for the highest altitude in orbit, in analogy with the more common term apogee, which applies for Earth orbits. (Demeter is the Greek counterpart of the Roman goddess Ceres.) Dawn was at its apodemeter of 46,800 miles (75,400 kilometers) on March 18. For more on Dawn’s approach trajectory, see the overall description and figures from other perspectives in November (including the motion into and out of this flat depiction), further details (including the OpNavs) in February and an animation in March. Image credit: NASA/JPL

The dwarf planet is around 590 miles (950 kilometers) in diameter (like Earth and other planets, however, it is slightly wider at the equator than from pole to pole). At the spacecraft’s orbital altitude, it will appear to be the same size as a soccer ball seen from 10 feet (3 meters) away. Part of the basis upon which mission planners chose this distance for the first mapping campaign is that the visible disc of Ceres will just fit in the camera’s field of view. All the pictures taken at lower altitudes will cover a smaller area (but will be correspondingly more detailed). The photos from RC3 will be 3.4 times sharper than those in RC2.

There will be work to do before photography begins however. The first order of business after concluding ion thrusting will be for the flight team to perform a quick navigational update (this time, using only the radio signal) and transmit any refinements (if necessary) in Dawn’s orbital parameters, so it always has an accurate knowledge of where it is. (These will not be adjustments to the orbit but rather a precise mathematical description of the orbit it achieved.) Controllers will also reconfigure the spacecraft for its intensive observations, which will commence on April 24 as it passes over the south pole and to the night side again.

As at Vesta, even though half of each circular orbit will be over the night side of Ceres, the spacecraft itself will never enter the shadows. The operations team has carefully designed the orbits so that at Dawn’s altitude, it remains illuminated by the sun, even when the land below is not.

It may seem surprising (or even be surprising) that Dawn will conduct measurements when the ground directly beneath it is hidden in the deep darkness of night. To add to the surprise, these observations were not even envisioned when Dawn’s mission was designed, and it did not perform comparable measurements during its extensive exploration of Vesta in 2011-2012.

This artist's concept shows NASA's Dawn spacecraft arriving at the dwarf planet Ceres (lower right). Dawn travels through space using a technology called ion propulsion, in which ions are accelerated out of an engine, giving the spacecraft thrust. The xenon ions glow with blue light.
This artist’s concept shows Dawn thrusting with its center ion engine high above the night side of Ceres, which displays only a narrow crescent below the spacecraft. The gentle but efficient thrust allows Dawn to change the shape of its orbit. It will complete this first phase of orbital maneuvering on April 23 when it achieves RC3 orbit. Image credit: NASA/JPL-Caltech

The measurements on the night side will serve several purposes. One of the many sophisticated techniques scientists use to elucidate the nature of planetary surfaces is to measure how much light they reflect at different angles. Over the course of the next year, Dawn will acquire tens of thousands of pictures from the day side of Ceres, when, in essence, the sun is behind the camera. When it is over the night side in RC3, carefully designed observations of the lit terrain (with the sun somewhat in front of the camera, although still at a safe angle) will significantly extend the range of angles.

In December, we described the fascinating discovery of an extremely diffuse veil of water vapor around Ceres. How the water makes its way from the dwarf planet high into space is not known. The Dawn team has devised a plan to investigate this further, even though the tiny amount of vapor was sighted long after the explorer left Earth equipped with sensors designed to study worlds without atmospheres.

It is worth emphasizing that the water vapor is exceedingly tenuous. Indeed, it is much less dense than Earth’s atmosphere at altitudes above the International Space Station, which orbits in what most people consider to be the vacuum of space. Our hero will not need to deploy its umbrella. Even comets, which are miniscule in comparison with Ceres, liberate significantly more water.

There may not even be any water vapor at all now because Ceres is farther from the sun than when the Herschel Space Observatory saw it, but if there is, detecting it will be very challenging. The best method to glimpse it is to look for its subtle effects on light passing through it. Although Dawn cannot gaze directly at the sun, it can look above the lit horizon from the night side, searching intently for faint signs of sunlight scattered by sparse water molecules (or perhaps dust lofted into space with them).

For three days in RC3 after passing over the south pole, the probe will take many pictures and visible and infrared spectra as it watches the slowly shrinking illuminated crescent and the space over it. When the spacecraft has flown to about 29 degrees south latitude over the night side, it will no longer be safe to aim its sensitive instruments in that direction, because they would be too close to the sun. With its memory full of data, Dawn will turn to point its main antenna toward distant Earth. It will take almost two days to radio its findings to NASA’s Deep Space Network. Meanwhile, the spacecraft will continue northward, gliding silently high over the dark surface.

On April 28, it will rotate again to aim its sensors at Ceres and the space above it, resuming measurements when it is about 21 degrees north of the equator and continuing almost to the north pole on May 1. By the time it turns once again to beam its data to Earth, it will have completed a wealth of measurements not even considered when the mission was being designed.

Loyal readers will recall that Dawn has lost two of its four reaction wheels, gyroscope-like devices it uses to turn and to stabilize itself. Although such a loss could be grave for some missions, the operations team overcame this very serious challenge. They now have detailed plans to accomplish all of the original Ceres objectives regardless of the condition of the reaction wheels, even the two that have not failed (yet). It is quite a testament to their creativity and resourcefulness that despite the tight constraints of flying the spacecraft differently, the team has been able to add bonus objectives to the mission.

Some might see a pancake, and others a sand dollar, in this new image of dwarf planet Ceres from NASA's Dawn mission.
Dawn had this view of Ceres on Feb. 19 at a distance of 28,000 miles (46,000 kilometers). Among the puzzling features is the large structure below and to the right of center. Pictures in RC3 will be more than three times sharper. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dawn will finish transmitting its data after its orbit takes it over the north pole and to the day side of Ceres again. For three periods during its gradual flight of more than a week over the illuminated landscape, it will take pictures (in visible and near-infrared wavelengths) and spectra. Each time, it will look down from space for a full Cerean day, watching for more than nine hours as the dwarf planet pirouettes, as if showing off to her new admirer. As the exotic features parade by, Dawn will faithfully record the sites.

It is important to set the camera exposures carefully. Most of the surface reflects nine percent of the sunlight. (For comparison, the moon reflects 12 percent on average, although as many Earthlings have noticed, there is some variation from place to place. Mars reflects 17 percent, and Vesta reflects 42 percent. Many photos seem to show that your correspondent’s forehead reflects about 100 percent.) But there are some small areas that are significantly more reflective, including the two most famous bright spots. Each spot occupies only one pixel (2.7 miles, or 4.3 kilometers across) in the best pictures so far. If each bright area on the ground is the size of a pixel, then they reflect around 40 percent of the light, providing the stark contrast with the much darker surroundings. When Dawn’s pictures show more detail, it could be that they will turn out to be even smaller and even more reflective than they have appeared so far. In RC3, each pixel will cover 0.8 miles (1.3 kilometers). To ensure the best photographic results, controllers are modifying the elaborate instructions for the camera to take pictures of the entire surface with a wider range of exposures than previously planned, providing high confidence that all dark and all bright areas will be revealed clearly.

Dawn will observe Ceres as it flies from 45 degrees to 35 degrees north latitude on May 3-4. Of course, the camera’s view will extend well north and south of the point immediately below it. (Imagine looking at a globe. Even though you are directly over one point, you can see a larger area.) The territory it will inspect will include those intriguing bright spots. The explorer will report back to Earth on May 4-5. It will perform the same observations between 5 degrees north and 5 degrees south on May 5-6 and transmit those findings on May 6-7. To complete its first global map, it will make another full set of measurements for a Cerean day as it glides between 35 degrees and 45 degrees south on May 7.

By the time it has transmitted its final measurements on May 8, the bounty from RC3 may be more than 2,500 pictures and two million spectra. Mission controllers recognize that glitches are always possible, especially in such complex activities, and they take that into account in their plans. Even if some of the scheduled pictures or spectra are not acquired, RC3 should provide an excellent new perspective on the alien world, displaying details three times smaller than what we have discerned so far.

Dawn activated its gamma ray spectrometer and neutron spectrometer on March 12, but it will not detect radiation from Ceres at this high altitude. For now, it is measuring space radiation to provide context for later measurements. Perhaps it will sense some neutrons in the third mapping orbit this summer, but its primary work to determine the atomic constituents of the material within about a yard (meter) of the surface will be in the lowest altitude orbit at the end of the year.

Illustration of Dawn’s four mapping orbits
Dawn’s four mapping orbits, shown to scale in altitude with the size of Ceres, which is about 590 miles (950 kilometers) in diameter. (Note: colors of the orbits here are only approximate.) The table below includes links to descriptions of the activities in each orbit. Image credit: NASA/JPL-Caltech

Dawn will conduct its studies from three lower orbital altitudes after RC3, taking advantage of the tremendous maneuverability provided by ion propulsion to spiral from one to another. We presented previews last year of each phase, and as each approaches, we will give still more up-to-date details, but now that Dawn is in orbit, let’s summarize them here. Of course, with complicated operations in the forbidding depths of space, there are always possibilities for changes, especially in the schedule. The team has developed an intricate but robust and flexible plan to extract as many secrets from Ceres as possible, and they will take any changes in stride.

Each orbit is designed to provide a better view than the one before, and Dawn will map the orb thoroughly while at each altitude. The names for the orbits – rotation characterization 3 (RC3); survey; high altitude mapping orbit (HAMO); and low altitude mapping orbit (LAMO) – are based on ancient ideas, and the origins 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 blogs. That ensures consistency with other Dawn project communications. After all, what is important is not what the different orbits are called but rather what amazing new discoveries each one enables.

The robotic explorer will make many kinds of measurements with its suite of powerful instruments. As one indication of the improving view, this table includes the resolution of the photos, and the ever finer detail may be compared with the pictures during the approach phase. For another perspective, we extend the soccer ball analogy above to illustrate how large Ceres will appear to be from the spacecraft’s orbital vantage point.

chart showing what Dawn will see at various orbits about Ceres

As Dawn orbits Ceres, together they orbit the sun. Closer to the master of the solar system, Earth (with its own retinue, including the moon and many artificial satellites) travels faster in its heliocentric orbit because of the sun’s stronger gravitational pull at its location. In December, Earth was on the opposite side of the sun from Dawn, and now the planet’s higher speed is causing their separation to shrink. Earth will get closer and closer until July 22, when it will pass on the inside track, and the distance will increase again.

In the meantime, on April 12, Dawn will be equidistant from the sun and Earth. The spacecraft will be 2.89 AU or 269 million miles (433 million kilometers) from both. At the same time, Earth will be 1.00 AU or 93.2 million miles (150 million kilometers) from the sun.

Illustration showing the positions of Earth, Mars, Vesta and Ceres from the sun to Dawn
Illustration of the relative locations (but not sizes) of Earth, the sun, Dawn and Ceres on April 12, 2015. (Earth and the sun are at that location every April 12.) The distance from Earth to Dawn is the same as the distance from the sun to Dawn. The images are superimposed on the trajectory for the entire mission, showing the positions of Earth, Mars, Vesta, and Ceres at milestones during Dawn’s voyage. Compare this to the arrangement in December, when Earth and Dawn were on opposite sides of the sun. Image credit: NASA/JPL-Caltech

It will be as if Dawn is at the tip of a giant celestial arrowhead, pointing the way to a remarkable solar system spectacle. The cosmos should take note! Right there, a sophisticated spaceship from Earth is gracefully descending on a blue-green beam of xenon ions. Finally, the dwarf planet beneath it, a remote remnant from the dawn of the solar system, is lonely no more. Almost 4.6 billion years after it formed, and 214 years after inquisitive creatures on a distant planet first caught sight of it, a mysterious world is still welcoming the new arrival. And as Dawn prepares to settle into its first close orbit, ready to discover secrets Ceres has kept for so long, everyone who shares in the thrill of this grand and noble adventure eagerly awaits its findings. Together, we look forward to the excitement of new knowledge, new insight and new fuel for our passionate drive to explore the universe.

Dawn is 35,000 miles (57,000 kilometers) from Ceres, or 15 percent of the average distance between Earth and the moon. It is also 3.04 AU (282 million miles, or 454 million kilometers) from Earth, or 1,120 times as far as the moon and 3.04 times as far as the sun today. Radio signals, traveling at the universal limit of the speed of light, take 51 minutes to make the round trip.

Dr. Marc D. Rayman
6:00 p.m. PDT March 31, 2015

› Read more entries from Marc Rayman's Dawn Journal


  • Marc Rayman

Animation of the Soil Moisture Active Passive spacecraft spinning its antenna while orbiting Earth.Youtube video

This Thursday, March 19, NASA's latest mission will begin preparation for its next great milestone: making the wicked-amazing antenna rotate.

A number of spacecraft have rotating parts, such as the RapidScat mission and the Global Precipitation Measurement (GPM) mission, but those don't hold a candle to the dynamics of Soil Moisture Active Passive (SMAP).

SMAP's antenna is 20 feet in diameter. The larger the antenna, the more complex its behavior can be, which makes it more difficult to control. Just imagine swinging a 20-foot baseball bat over your head. Yikes!

Right now the antenna is locked in position until the mission "ops" (operations) team completes its checks of the entire instrument's function and confirms operability. They have taken measurements with the radar and the radiometer. They know the instruments are working by comparing the measurements to how they were tested on the ground before launch. The signals look appropriate; they're seeing what's expected. But the antenna's fixed position means it's measuring only a small strip of the ground below.

Once the antenna starts to spin, we'll be able to measure a much larger area and monitor soil moisture around the entire Earth every two to three days.

These are the three steps to achieving "spin up":

1. Engineers unlock the antenna.

2. A few days later, they spin the antenna slowly.

3. They gradually spin it faster.

At each step, they'll verify how it's performing. The engineers will then conduct a more comprehensive checkout of the instrument's systems. With the antenna spinning, they'll get to see the instrument's full performance for the first time.

After the spinning checkouts are completed ... Voilà! Bibbidi bobbidi boo! SMAP will start mapping global soil moisture and return data!

I look forward to your comments.

- Laura

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Animated gif of Ceres rotating as imaged by Dawn

Dear Unprecedawnted Readers,

Since its discovery in 1801, Ceres has been known as a planet, then as an asteroid, and later as a dwarf planet. Now, after a journey of 3.1 billion miles (4.9 billion kilometers) and 7.5 years, Dawn calls it “home.”

Earth’s robotic emissary arrived at about 4:39 a.m. PST today. It will remain in residence at the alien world for the rest of its operational life, and long, long after.

Before we delve into this unprecedented milestone in the exploration of space, let’s recall that even before reaching orbit, Dawn started taking pictures of its new home. Last month we presented the updated schedule for photography. Each activity to acquire images (as well as visible spectra and infrared spectra) has executed smoothly and provided us with exciting and tantalizing new perspectives.

While there are countless questions about Ceres, the most popular now seems to be what the bright spots are. It is impossible not to be mesmerized by what appear to be glowing beacons, shining out across the cosmic seas from the uncharted lands ahead. But the answer hasn’t changed: we don’t know. There are many intriguing speculations, but we need more data, and Dawn will take photos and myriad other measurements as it spirals closer and closer during the year. For now, we simply know too little.

For example, some people ask if those spots might be lights from an alien city. That’s ridiculous! At this early stage, how could Dawn determine what kinds of groupings Cereans live in? Do they even have cities? For all we know, they may live only in rural communities, or perhaps they only have large states.

What we already know is that in more than 57 years of space exploration, Dawn is now the only spacecraft ever to orbit two extraterrestrial destinations. A true interplanetary spaceship, Dawn left Earth in Sep. 2007 and traveled on its own independent course through the solar system. It flew past Mars in Feb. 2009, robbing the red planet of some of its own orbital energy around the sun. In July 2011, the ship entered orbit around the giant protoplanet Vesta, the second most massive object in the main asteroid belt between Mars and Jupiter. (By the way, Dawn’s arrival at Vesta was exactly one Vestan year ago earlier this week.) It conducted a spectacular exploration of that fascinating world, showing it to be more closely related to the terrestrial planets (including Earth, home to many of our readers) than to the typical objects people think of as asteroids. After 14 months of intensive operations at Vesta, Dawn climbed out of orbit in Sep. 2012, resuming its interplanetary voyage. Today it arrived at its final destination, Ceres, the largest object between the sun and Pluto that had not previously been visited by a spacecraft. (Fortunately, New Horizons is soon to fly by Pluto. We are in for a great year!)

What was the scene like at JPL for Dawn’s historic achievement? It’s easy to imagine the typical setting in mission control. The tension is overwhelming. Will it succeed or will it fail? Anxious people watch their screens, monitoring telemetry carefully, frustrated that there is nothing more they can do now. Nervously biting their nails, they are thinking of each crucial step, any one of which might doom the mission to failure. At the same time, the spacecraft is executing a bone-rattling, whiplash-inducing burn of its main engine to drop into orbit. When the good news finally arrives that orbit is achieved, the room erupts! People jump up and down, punch the air, shout, tweet, cry, hug and feel the tremendous relief of overcoming a huge risk. You can imagine all that, but that’s not what happened.

If you had been in Dawn mission control, the scene would have been different. You would mostly be in the dark. (For your future reference, the light switches are to the left of the door.) The computer displays would be off, and most of the illumination would be from the digital clock and the string of decorative blue lights that indicate the ion engine is scheduled to be thrusting. You also would be alone (at least until JPL Security arrived to escort you away, because you were not cleared to enter the room, and, for that matter, how did you get past the electronic locks?). Meanwhile, most of the members of the flight team were at home and asleep! (Your correspondent was too, rare though that is. When Dawn entered orbit around Vesta, he was dancing. Ceres’ arrival happened to be at a time less conducive to consciousness.)

Why was such a significant event treated with somnolence? It is because Dawn has a unique way of entering orbit, which is connected with the nature of the journey itself. We have discussed some aspects of getting into orbit before (with this update to the nature of the approach trajectory). Let’s review some of it here.

It may be surprising that prior to Dawn, no spacecraft had even attempted to orbit two distant targets. Who wouldn’t want to study two alien worlds in detail, rather than, as previous missions, either fly by one or more for brief encounters or orbit only one? A mission like Dawn’s is an obvious kind to undertake. It happens in science fiction often: go somewhere, do whatever you need to do there (e.g., beat someone up or make out with someone) and then boldly go somewhere else. However, science fact is not always as easy as science fiction. Such missions are far, far beyond the capability of conventional propulsion.

Deep Space 1 (DS1) blazed a new trail with its successful testing of ion propulsion, which provides 10 times the efficiency of standard propulsion, showing on an operational interplanetary mission that the advanced technology really does work as expected. (This writer was fortunate enough to work on DS1, and he even documented the mission in a series of increasingly wordy blogs. But he first heard of ion propulsion from the succinct Mr. Spock and subsequently followed its use by the less logical Darth Vader.)

Global mosaic of craters, mysterious bright spots and other intriguing features on Ceres
Dawn observed Ceres throughout a full nine-hour rotation of the dwarf planet, yielding this global mosaic of craters, mysterious bright spots and other intriguing features. The photos were taken on Feb. 19 from a distance of about 28,000 miles (46,000 kilometers). Ceres has about 38 percent of the area of the continental United States. The imaging session was known as RC2. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dawn’s ambitious expedition would be truly impossible without ion propulsion. (For a comparison of chemical and ion propulsion for entering orbit around Mars, an easier destination to reach than either Vesta or Ceres, visit this earlier log.) So far, our advanced spacecraft has changed its own velocity by 23,800 mph (38,400 kilometers per hour) since separating from its rocket, far in excess of what any other mission has achieved propulsively. (The previous record was held by DS1.)

Dawn is exceptionally frugal in its use of xenon propellant. In this phase of the mission, the engine expends only a quarter of a pound (120 grams) per day, or the equivalent of about 2.5 fluid ounces (75 milliliters) per day. So although the thrust is very efficient, it is also very gentle. If you hold a single sheet of paper in your hand, it will push on your hand harder than the ion engine pushes on the spacecraft at maximum thrust. At today’s throttle level, it would take the distant explorer almost 11 days to accelerate from zero to 60 mph (97 kilometers per hour). That may not evoke the concept of a drag racer. But in the zero-gravity, frictionless conditions of spaceflight, the effect of this whisper-like thrust can build up. Instead of thrusting for 11 days, if we thrust for a month, or a year, or as Dawn already has, for more than five years, we can achieve fantastically high velocity. Ion propulsion delivers acceleration with patience.

Most spacecraft coast most of the time, following their repetitive orbits like planets do. They may use the main engine for a few minutes or perhaps an hour or two throughout the entire mission. With ion propulsion, in contrast, the spacecraft may spend most of its time in powered flight. Dawn has flown for 69% of its time in space emitting a cool blue-green glow from one of its ion engines. (With three ion engines, Dawn outdoes the Star Wars TIE (twin ion engine) fighters.)

OpNav 5 images zoomed in
As Dawn maneuvers into orbit, its trajectory takes it to the opposite side of Ceres from the sun, providing these crescent views. These pictures (part of the OpNav 5 activity), were taken on March 1 at a distance of 30,000 miles (49,000 kilometers). Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The robotic probe uses its gentle thrust to gradually reshape its path through space rather than simply following the natural course that a planet would. After it escaped from Vesta’s gravitational clutches, it slowly spiraled outward from the sun, climbing the solar system hill, making its heliocentric orbit more and more and more like Ceres’. By the time it was in the vicinity of the dwarf planet today, both were traveling around the sun at more than 38,600 mph (62,100 kilometers per hour). Their trajectories were nearly identical, however, so the difference in their speeds was only 100 mph (160 kilometers per hour), or less than 0.3 percent of the total. Flying like a crackerjack spaceship pilot, Dawn elegantly used the light touch of its ion engine to be at a position and velocity that it could ease gracefully into orbit. At a distance of 37,700 miles (60,600 kilometers), Ceres reached out and tenderly took the newcomer from Earth into its permanent gravitational embrace.

If you had been in space watching the event, you would have been cold, hungry and hypoxic. But it would not have looked much different from the 1,885 days of ion thrust that had preceded it. The spacecraft was perched atop its blue-green pillar of xenon ions, patiently changing its course, as it does for so much of quiet cruise. But now, at one moment it was flying too fast for Ceres’ gravity to hang on to it, and the next moment it had slowed just enough that it was in orbit. Had it stopped thrusting at that point, it would have continued looping around the dwarf planet. But it did not stop. Instead, it is working now to reshape its orbit around Ceres. As we saw in November, its orbital acrobatics first will take it up to an altitude of 47,000 miles (75,000 kilometers) on March 19 before it swoops down to 8,400 miles (13,500 kilometers) on April 23 to begin its intensive observations in the orbit designated RC3.

In fact, Dawn’s arrival today really is simply a consequence of the route it is taking to reach that lower orbit next month. Navigators did not aim for arriving today. Rather, they plotted a course that began at Vesta and goes to RC3 (with a new design along the way), and it happens that the conditions for capture into orbit occurred this morning. As promised last month, we present here a different view of the skillful maneuvering by this veteran space traveler.

This animation gives a three-dimensional view of Dawn’s complex approach to Ceres. The spacecraft deftly maneuvers into orbit with its ion propulsion system, flying to RC3 orbit, which is achieved when the thrust is turned off. (The size of Ceres is exaggerated compared to the size of the orbit here.) At the end, the viewpoint shifts to provide another perspective on the unique trajectory.

If Dawn had stopped thrusting before Ceres could exert its gravitational control, it wouldn’t have flown very far away. The spacecraft had already made their paths around the sun very similar, and the ion propulsion system provides such exceptional flexibility to the mission that controllers could have guided it into orbit some other time. This was not a one-time, all-or-nothing event.

So the flight team was not tense. They had no need to observe it or make a spectacle out of it. Mission control remained quiet. The drama is not in whether the mission will succeed or fail, in whether a single glitch could cause a catastrophic loss, in whether even a tiny mistake could spell doom. Rather, the drama is in the opportunity to unveil the wonderful secrets of a fascinating relict from the dawn of the solar system more than 4.5 billion years ago, a celestial orb that has beckoned for more than two centuries, the first dwarf planet discovered.

Dawn usually flies with its radio transmitter turned off (devoting its electricity instead to the power-hungry ion engine), and so it entered orbit silently. As it happened, a routine telecommunications session was scheduled about an hour after attaining orbit, at 5:36 a.m. PST. (It’s only coincidence it was that soon. At Vesta, it was more than 25 hours between arrival and the next radio contact.) For primary communications, Dawn pauses thrusting to point its main antenna to Earth, but other times, as in this case, it is programmed to use one of its auxiliary antennas to transmit a weaker signal without stopping its engine, whispering just enough for engineers to verify that it remains healthy.

The Deep Space Network’s exquisitely sensitive 230-foot (70-meter) diameter antenna in Goldstone, Calif., picked up the faint signal from across the solar system on schedule and relayed it to Dawn mission control. One person was in the room (and yes, he was cleared to enter). He works with the antenna operator to ensure the communications session goes smoothly, and he is always ready to contact others on the flight team if any anomalies arise. In this case, none did, and it was a quiet morning as usual. The mission director checked in with him shortly after the data started to trickle in, and they had a friendly, casual conversation that included discussing some of the telemetry that indicated the spacecraft was still performing its routine ion thrusting. The determination that Dawn was in orbit was that simple. Confirming that it was following its flight plan was all that was needed to know it had entered orbit. This beautifully choreographed celestial dance is now a pas de deux.

As casual and tranquil as all that sounds, and as logical and systematic as the whole process is, the reality is that the mission director was excited. There was no visible hoopla, no audible fanfare, but the experience was powerful fuel for the passionate fires that burn within.

As soundlessly as a spacecraft gliding through the void, the realization emerges …

Dawn made it!!

It is in orbit around a distant world!!

Yes, it’s clear from the technical details, but it is more intensely reflected in the silent pounding of a heart that has spent a lifetime yearning to know the cosmos. Years and years of hard work devoted to this grand undertaking, constant hopes and dreams and fears of all possible futures, uncounted challenges (some initially appearing insurmountable) and a seeming infinitude of decisions along the way from early concepts through a real interplanetary spacecraft flying on an ion beam beyond the sun.

And then, a short, relaxed chat over a few bits of routine data that report the same conditions as usual on the distant robot. But today they mean something different.

They mean we did it!!

Everyone on the team will experience the news that comes in a congratulatory email in their own way, in the silence and privacy of their own thoughts. But it means the same to everyone.

We did it!!

And it’s not only the flight team. Humankind!! With our relentless curiosity, our insatiable hunger for knowledge, our noble spirit of adventure, we all share in the experience of reaching out from our humble home to the stars.

Together, we did it!!!

It was a good way to begin the day. It was Dawn at Ceres.

This video overview of the mission at Ceres is a great way to start your day, but you can enjoy it at any time.

Let’s bring into perspective the cosmic landscape on which this remarkable adventure is now taking place. Imagine Earth reduced to the size of a soccer ball. On this scale, the International Space Station would orbit at an altitude of a bit more than one-quarter of an inch (seven millimeters). The moon would be a billiard ball almost 21 feet (6.4 meters) away. The sun, the conductor of the solar system orchestra, would be 79 feet (24 meters) across at a distance of 1.6 miles (2.6 kilometers). But even more remote, Dawn would be 5.3 miles (8.6 kilometers) away. (Just a few months ago, when the spacecraft was on the opposite side of the sun from Earth, it would have been more than six miles, or almost 10 kilometers, from from the soccer ball.) Tremendously far now from its erstwhile home, it would be only a little over a yard (a meter) from its new residence. (By the end of this year, Dawn will be slightly closer to it than the space station is to Earth, a quarter of an inch, or six millimeters.) That distant world, Ceres, the largest object between Mars and Jupiter, would be five-eighths of an inch (1.6 centimeters) across, about the size of a grape. Of course a grape has a higher water content than Ceres, but we can be sure that exploring this intriguing world of rock and ice will be much sweeter!

As part of getting to know its new neighborhood, Dawn has been hunting for moons of Ceres. Telescopic studies had not revealed any, but if there were a moon smaller than about half a mile (one kilometer), it probably would not have been discovered. The spacecraft’s unique vantage point provides an opportunity to look for any that might have escaped detection. Many pictures have been taken specifically for this purpose, and scientists scrutinize them and all of the other photographs for any indication of moons. While the search will continue, so far, no picture has shown evidence of companions orbiting Ceres.

And yet we know that as of today, Ceres most certainly does have one. Its name is Dawn!

Dawn is 37,800 miles (60,800 kilometers) from Ceres, or 16 percent of the average distance between Earth and the moon. It is also 3.33 AU (310 million miles, or 498 million kilometers) from Earth, or 1,230 times as far as the moon and 3.36 times as far as the sun today. Radio signals, traveling at the universal limit of the speed of light, take 55 minutes to make the round trip.

Dr. Marc D. Rayman
6:00 a.m. PST March 6, 2015

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Illustration of a bird and outlined wings

Unless you call yourself a rocket scientist, you probably don’t think your daily routine has much in common with flight software engineering. But you would be wrong.

Flight software engineers write computer code for NASA spacecraft, which is complicated because—hello—flying spacecraft into space is complicated.

Flight software runs the instruments and sensors that operate thermal control, spin stabilization on all three axes, uplink and downlink to communicate with spacecraft, data collection and handling, a cruise phase, a descent phase and sometimes a “landing on the surface of a planet” phase. And some of this happens simultaneously. (And I thought feeding the cat and dog at the same time was rough.)

If the spacecraft is far away, like, dude, on Mars or beyond, there’s no controlling it from the ground with a joystick, so the software has to be written to allow the spacecraft to run autonomously.

But the experiences of a flight-software-engineering person* are actually the same as the experiences of a regular-person person, from planning a family reunion, to cleaning the garage, to simply shopping for tonight’s dinner. If you skip the bits about the flying, disregard the software and pay no attention to the engineering, then what you’re left with is some amazingly useful life lessons:

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