High gain antenna tower at JPL

In the early 1960s, Mesa Road at NASA's Jet Propulsion Laboratory had not yet been built. Access to buildings on the mesa, like the High Gain Antenna Tower in this photo, was through the residential neighborhood north of JPL.

The antenna tower was built at the end of 1961, and was used by the Telecommunications Division in testing prototypes and various configurations of Deep Space Network antenna equipment. The platform was designed to reduce ground reflections from the sides and bottom of the adjacent canyon.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.


  • Julie Cooper

M/V Cape Race at Kullorsuaq, Greenland

This morning when I told someone I’d interviewed NASA oceanographer Josh Willis for this blog, they replied, “Isn’t Josh Willis a climatologist?”

“Aha!” I said. “That’s a problem. Not knowing that Earth’s ocean is responsible for controlling the climate is major. Oceanographers are climatologists.”

I mean, look, the ocean covers 71 percent of the planet’s surface, and 71 percent is like, duh, a lot. The ocean, in fact, is so important that a better name for our planet would have been “Ocean” rather than “Earth” — even though our species spends most of its time on boring old land. #sorrynotsorry, geologists.

And you might not realize this because it’s so familiar, but water is crazy. It has this unusual property, called “high heat capacity,” that gives it the ability to hold a stable temperature. It resists heating and cooling. Water will absorb a lot of energy before it changes temperature even a little bit.

And this property of water, this high heat capacity, is what makes life on our planet possible. It’s also what controls and moderates our climate, which is why our ocean, more than our atmosphere, is responsible for creating a stable climate on Earth.

So this is the reason oceanographers are climatologists. It’s also part of the reason Willis chose to name his new science project Oceans Melting Greenland (OMG). He hopes that people everywhere will recognize the role Earth’s ocean plays in controlling the climate and to say to the world, “Hey! The ocean is eating away at the ice sheet! The ocean is playing a huge role in melting the glaciers; it's melting Greenland!”

Remember I just told you water absorbs a lot of energy before it heats up? Well, humans have added so much energy to the Earth system by burning fossil fuels that we have heated the ocean. And now that we’ve warmed it up, you guessed it: The water is in no hurry to change back, so we’re going to be stuck with this warmer water for a very long time. And, says Willis, “Since Greenland is one of the last two remaining ice sheets on the planet, its fate is intertwined with how much destruction we’re going to have with climate change.” If you just said “OMG,” you would be right.

But if you think scientists know everything there is to know about the ocean, you would be very wrong. Willis and his team want to find out more about the complicated geometry (the shape and depth of the seafloor) around Greenland to understand the interaction between the water and ice so that we can find out how fast the glaciers are melting.

graphic showing M/V Cape Race route

M/V Cape Race ship track for phase 1 of 2015 OMG survey. Credit: Ian Fenty

This summer OMG used a ship, M/V Cape Race, to sail right up the narrow fjords on the continental shelf surrounding Greenland to the places where the 4- to 5-degree Atlantic Ocean water meets the bottoms of the frozen zero degree glaciers. The Cape Race used a multibeam echo sounder to map undersea canyons where the warm seawater comes in contact with and melts the glaciers. Willis followed the ship’s path via smartphone, sitting up in his PJs at two o’clock in the morning and uttering a variety of exclamations, including “OMG, turn left, left!”

Next year, the Cape Race will continue to make its way around Greenland, mapping the depth of the seafloor near the fjords, while Willis joins his team in the field flying on NASA’s G-III plane.

“OMG is a big picture project,” he told me. ”We want to see what’s happening in the ocean on the large scale and what’s happening to the ice sheet on the largest scales.”

In the spring, the NASA aircraft, with Willis aboard, will measure how much Greenland glaciers are thinning using the Glacier and Ice Surface Topography Interferometer (GLISTIN-A) instrument. They plan to deploy temperature and salinity probes in the summer. “In most of these places, there’s been no temperature and salinity data collected,” Willis said pausing, “ever.” Over the next five years, they will continue to monitor the ice sheet, asking, “When the water is this warm, how much ice melts?”

Willis knows “OMG” is a campy name for a NASA mission that makes light of a serious subject. “It’s easier to accept something as a reality when you can laugh at it, and accepting reality is a step towards making a change,” he said, explaining that if he was bummed out about climate change all the time, he would be stuck. “Humor makes it tolerable.”

Hopefully, when you find out about Oceans Melting Greenland, you’ll respond in the only way that’s appropriate: “OMG!”

Find out more about Oceans Melting Greenland here, here and here.

View an infographic about the mission.

Thank you for reading, sharing and commenting.


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1997 vs. 2015 side by side comparisons of Pacific Ocean sea surface height

“The water is soooo warm!”

That sentence keeps popping out of Angelenos' mouths. It’s practically impossible to stick a toe into the California Pacific Ocean without making some sort of immediate involuntary exclamation regarding the water temperature. And the water has been unbelievably warm lately. The surf zone is full of swimmers frolicking in the waves. And even my cold-water averse puppy is now joyously prancing on his skinny little legs through the surf.

But along with the in-and-out, back-and-forth of the waves, my own moments of beach-ly delight also have an up-and-down quality. See, every time I stroll across the sand, I notice trash. Some pieces of trash are large items that people have obviously left on purpose, too neglectful to carry them away. Other pieces are small bits of plastic: a torn shred of wrapper, a crumb of rubber band that accidentally got away. I can’t help myself from noticing it. And I can’t help myself from picking it up, every piece I see, walking it over to a trash can, and throwing it in. When I see a piece of beach trash, nothing in me will allow me to walk past it. I can’t not pick it up.

A few days ago, as the sun was setting and most of the people had gone, I saw a seagull with a water bottle in its mouth. It reminded me of my puppy, who loves to chew a water bottle. He’ll grab it and run gleefully in circles until he drops and gets busy on the cap. If I don’t take it off him, he will start to swallow the chewed pieces. The gull was doing the same thing, playing with the bottle near the edge of the water, pecking instead of chewing, but otherwise in the same bouncy mood. I chased him down, took the water bottle off him and recycled it.

So I left the beach with mixed feelings. I’m just one person on one beach for one day. What about the rest of the beaches? What about the other days? Who will pick up the plastic there?

I come to this blog with similar mixed feelings. The warm waves feel wonderful, but I know it’s warm because of El Niño, the global climate event that starts on the eastern side of the Pacific Ocean all the way from California down to Peru. El Niño is complicated. *Will it bring much-needed rain to the parched southwestern region of the United States and relieve us from this ongoing drought? Will it be too much rain all at one time? Will it cause flooding and landslides?

Even now, the warmer waters on our side of the Pacific are causing many species that thrive in cooler waters to struggle while warmer water species are temporarily moving in. Sure, it’s interesting to SCUBA dive and see tropical fish, but the sea lions who depend on cooler waters are hating it big time.

Up-and-down, back-and-forth, in-and-out.

I figured you wouldn’t want to read yet another depressing piece about how much we’re trashing our planet. So, in searching for something less dismal, I went to talk with Bill Patzert and Josh Willis, unarguably the world’s leading experts on El Niño, to see what they had to say about our current El Niño conditions (other than the fact that they’re making a swim more pleasant and bringing lots of pink clouds to our Southern California sunsets).

As I walked in, the two NASA oceanographers were in the middle of a discussion about the impact of El Niño rains on the amount of ocean trash. “Oh perfect,” I thought. “So I’m going with a trash-themed blog. Game on, Oscar the Grouch, game on.”

When I told them about my inability to walk past trash at the beach, Patzert said, “Our beaches have been exceptionally clean for over a decade now because we haven’t had a strong El Niño. As soon as those rains come, any trash hibernating in our storm sewers or on our streets will get flushed into the L.A. River and onto SoCal beaches.”

Woohoo, trash!! Too bad Oscar isn’t a sea monster. He’d be elated.

Find out more about El Niño and the NASA instruments that study the phenomenon from space here.

Thank you for your comments.


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*Some scientific info about El Niño: Most of the time, under normal ocean conditions, trade winds blow from the east side of the Pacific to the west side. These winds push surface water towards the Western Pacific near Asia and Australia where the warm water piles up. This Western Pacific Warm Pool contains some of the warmest ocean waters on the planet. Every decade or so, the trade winds soften and all that warm water that normally stays on the western side of the Pacific, sloshes back towards the east and we get a phenomenon known as El Niño. Since the Pacific Ocean takes up about half of planet Earth, it has the potential to affect global weather patterns. A strong El Niño can bring warm moist conditions to the West Coasts of the Americas, while leaving Australia and Southeast Asia unusually dry. So far, the 2015-2016 El Niño is shaping up to be an exceptionally strong one.



Three workers in the Echo Station Control Room

This April 1962 photo of Deep Space Station 12 (DSS-12) in Goldstone, California, was featured in Space Programs Summary 37-15, Volume 3–The Deep Space Instrumentation Facility. The 85-foot (26-meter) Echo antenna can be seen through the window of the control room, and three unidentified men are at the controls. The Echo site was named for its support of Project Echo, an experiment that transmitted voice communications coast to coast by bouncing signals off the surface of a passive balloon-type satellite. The antenna was moved six miles in June 1962 to the Venus site (DSS-13) and in 1979 it was extended to 34 meters in diameter.

The bimonthly Space Programs Summary, or SPS, is an excellent source of information about JPL missions and related research from February 1959 to October 1970. In 1970, the SPS series was replaced by the Technical Reports (32-1 to 32-1606) and other report series.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.


  • Julie Cooper

Video animation of various views of CeresYoutube video

Dear Unhesidawntingly Enthusiastic Readers,

An ambitious explorer from Earth is gaining the best views ever of dwarf planet Ceres. More than two centuries after its discovery, this erstwhile planet is now being mapped in great detail by Dawn.

The spacecraft is engaged in some of the most intensive observations of its entire mission at Ceres, using its camera and other sensors to scrutinize the alien world with unprecedented clarity and completeness. At an average altitude of 915 miles (1,470 kilometers) and traveling at 400 mph (645 kilometers per hour), Dawn completes an orbit every 19 hours. The pioneer will be here for more than two months before descending to its final orbit.

The complex spiral maneuver down from the second mapping orbit at 2,700 miles (4,400 kilometers) went so well that Dawn arrived in this third mapping orbit on Aug. 13, which was slightly ahead of schedule. (Frequent progress of its descent, and reports on the ongoing work in the new orbit, are available here and on Twitter @NASA_Dawn.) It began this third mapping phase on schedule at 9:53:40 p.m. PDT on Aug. 17.

Map of Ceres with named craters
This map of Ceres shows the feature names approved by the International Astronomical Union as of August 14, 2015. We described the naming convention in December, and the most up-to-date list of names is here. (Click on the image for an enlarged view or go here for a similar version with other details.) Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

We had a detailed preview of the plans last year when Dawn was more than six thousand times farther from Ceres than it is today. (For reasons almost as old as Ceres itself, this phase is also known as the high altitude mapping orbit, or HAMO, although we have seen that it is the second lowest of the four mapping orbits.) Now let’s review what will happen, including a change mission planners have made since then.

The precious pictures and other data have just begun to arrive on Earth, and it is too soon to say anything about the latest findings, but stand by for stunning new discoveries. Actually, you could get pictures about as good as Dawn’s are now with a telescope 217 times the diameter of Hubble Space Telescope. An alternative is to build your own interplanetary spaceship, travel through the depths of space to the only dwarf planet in the inner solar system, and look out the window. Or go to the Ceres image gallery.

Dawn has already gained fabulous perspectives on this mysterious world from its first and second mapping orbits. Now at one third the altitude of the mapping campaign that completed in June, its view is three times as sharp. (Exploring the cosmos is so cool!) That also means each picture takes in a correspondingly smaller area, so more pictures are needed now to cover the entire vast and varied landscape. At this height, Dawn’s camera sees a square about 88 miles (140 kilometers) on a side, less than one percent of the more than one million square miles (nearly 2.8 million square kilometers). The orbital parameters were chosen carefully so that as Ceres rotates on its axis every nine hours (one Cerean day), Dawn will be able to photograph nearly all of the surface in a dozen orbital loops.

brightest spots on dwarf planet Ceres
The famous bright spots (or famously bright spots) in Occator crater, as viewed in the second mapping orbit. What will these mesmerizing features reveal with pictures three times sharper? We will know soon! And pictures from Dawn’s closest mapping orbit will display almost 12 times as much detail as seen here. Full image and caption. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

When Dawn explored the giant protoplanet Vesta from comparable orbits (HAMO1 in 2011 and HAMO2 in 2012), it pointed its scientific instruments at the illuminated ground whenever it was on the dayside. Every time its orbit took it over the nightside, it turned to point its main antenna at Earth to radio its findings to NASA’s Deep Space Network. As we explained last year, however, that is not the plan at Ceres, because of the failure of two of the ship’s reaction wheels. (By electrically changing the speed at which these gyroscope-like devices rotate, Dawn can turn or stabilize itself in the zero-gravity conditions of spaceflight.)

We discussed in January that the flight team has excogitated innovative methods to accomplish and even exceed the original mission objectives regardless of the condition of the wheels, even the two operable ones (which will not be used until the final mapping orbit). Dawn no longer relies on reaction wheels, although when it left Earth in 2007, they were deemed indispensable. The spacecraft’s resilience (which is a direct result of the team’s resourcefulness) is remarkable!

One of the many ingredients in the recipe for turning the potentially devastating loss of the wheels into a solid plan for success has been to rotate the spacecraft less frequently. Therefore, sometimes Dawn will wait patiently for half an orbit (almost 9.5 hours) as it flies above ground cloaked in the deep darkness of night, its instruments pointed at terrain they cannot detect. Other times, it will keep its antenna fixed on Earth without even glancing at the sunlit scenery below, because it can capture the views on other revolutions. This strategy conserves hydrazine, the conventional rocket propellant used by the small jets of the reaction control system in the absence of the wheels. It takes more time, but because Dawn is in orbit, time is not such a limited resource. It will take 12 passages over the illuminated hemisphere, each lasting nearly 9.5 hours, to bring the entirety of the landscape within view of its camera, but we will need a total of 14 full revolutions, or 11 days (29 Cerean days, for those of you using that calendar), to acquire and transmit all the data. The Dawn team calls this 11-day period “11 days,” or sometimes a “cycle.”

In quite a change from the days that there simply didn’t seem to be enough hydrazine onboard to accomplish all of the mission’s ambitious objectives, engineers and the spacecraft itself have collaborated to be so efficient with the precious molecules that they now have some to spare. Therefore, mission planners have recently decided to spend a few more in this mapping orbit. They have added extra turns to allow the robot to communicate with Earth during more of the transits over the nightside than they had previously budgeted. This means Dawn can send the contents of its computer memory to Earth more often and therefore have space to collect and store even more data than originally planned. An 11-day mapping cycle is going to be marvelously productive.

Dawn Survey Orbit Image 46
The conical mountain visible in the animation above is on the left of this photograph from the second mapping orbit. The mountain’s distinctive bright side is facing right. We presented two other perspectives of it in June. Scientists have recently refined their calculation of its height, now estimating that it towers an impressive four miles (six kilometers) above the surrounding terrain. In the third mapping orbit, Dawn will provide clearer views and a more accurate measurement of its elevation. The image below shows the mountain from still another perspective.
Full image and caption. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

But Dawn has goals still more ambitious than taking pictures and recording infrared and visible spectra of the lands passing underneath it. It will conduct six complete mapping cycles, each one looking at a slightly different angle. This will effectively yield stereo views, which when combined will make those flat images pop into full three dimensionality.

In its first mapping cycle, which is taking place now, the explorer aims its instruments straight down. For the second, it will keep the camera pointed a little bit back and to the left, making another full map but with a different perspective. For the third, it will look a little back and to the right. The fourth map will be viewing the scenery ahead and to the left. The fifth map will be of the terrain immediately ahead, and the sixth will be farther back than the third but not as far to the right.

In addition to the stereo pictures and the many spectra (which reveal the nature of the minerals as well as the surface temperature), Dawn will use the color filters in its camera to record the sights in visible and infrared wavelengths.

As always, mission planners schedule more observations than are needed, recognizing that glitches can occur on a complex and challenging expedition in the forbidding depths of space. So even if some data are not collected, the goals can still be accomplished.

The probe also will continue to acquire spectra both of neutrons and of gamma rays. It is unlikely to detect more than a whisper of neutrons from Ceres at this height, but the radiation coming from elsewhere in space now will serve as a useful calibration when it measures stronger nuclear emanations from one quarter the altitude starting in December, allowing scientists to inventory Ceres’ atomic constituents.

Precise measurements of Dawn’s radio signal will reveal more details of the dwarf planet’s gravitational field and hence the distribution of mass within. When the spacecraft is not aiming its main antenna at Earth, it will broadcast through one of its three auxiliary antennas, and the Deep Space Network will be listening (almost) continuously throughout the 84 orbits.

a conical mountain on Ceres
The same conical mountain pictured above can be seen on the left of this photograph. Some of the bright material outside Haulani crater is visible near the limb on the right edge. Full image and caption. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

As at Vesta, Dawn’s polar orbits are oriented so that the craft always keeps the sun in view, never entering Ceres’ shadow, even when it is nighttime on the ground below. But its course will take the robot out of sight from Earth occasionally, and the behemoth of rock and ice will block the radio signal. Of course, Dawn is quite accustomed to operating in radio silence. It follows timed instructions (called sequences) that cover a full mapping cycle, so it does not require constant contact. And in budgeting how much data Dawn can collect and transmit, mission planners have accounted for the amount of time Ceres will eclipse its view of Earth.

Thanks to the uniquely efficient and exceptionally gentle thrust of the ion engines, as well as the flexibility inherent in being in orbit, Dawn operations generally can be more leisurely than those with conventional chemical propulsion or missions that only fly past their targets rather than stay for as long as needed. In that spirit, controllers had allowed the time in the spacecraft’s main computer to drift off, as there was no need to keep it particularly accurate. But recently the clock was off by so much that they decided to correct it, so before the mapping began, they adjusted it by a whopping 0.983 seconds, eliminating a large (but still tolerable) offset.

Many residents of Earth’s northern hemisphere are completing their leisurely summer vacations. As we saw in February, Dawn has measured the orientation of Ceres’ spin axis and found that it is tipped about four degrees (compared with Earth’s axial tilt of 23 degrees). The sun then never moves very far from the dwarf planet’s equator, so seasonal variations are mild. Nevertheless, northern hemisphere summer (southern hemisphere winter) began on Ceres on July 24. Because Ceres takes longer to revolve around the sun than Earth, seasons last much longer. The next equinox won’t occur until Nov. 13, 2016, so there is still plenty of time to plan a summer vacation.

Meanwhile, Dawn is working tirelessly to reveal the nature of this complex, intriguing world. Now seeing the exotic sights with a shaper focus than ever, the probe’s meticulous mapping will provide a wealth of new data that scientists will turn into knowledge. And everyone who has ever seen the night sky beckon, everyone who has heard the universe’s irresistible invitation, and everyone who has felt the overpowering drive for a bold journey far from Earth shares in the experience of this remarkable interplanetary adventure.

Dawn is 905 miles (1,456 kilometers) from Ceres. It is also 2.06 AU (191 million miles, or 308 million kilometers) from Earth, or 775 times as far as the moon and 2.03 times as far as the sun today. Radio signals, traveling at the universal limit of the speed of light, take 34 minutes to make the round trip.

Dr. Marc D. Rayman
5:00 p.m. PDT August 21, 2015


  • Marc Rayman

Illustration of doors opening up onto a grassy field

“How difficult is it going to be to switch from a fossil fuel economy to a renewable energy economy?” asked a gentleman from the audience. I paused and took a deep breath.

I was giving a lecture about climate change at a retirement community, and I’d been thinking about my own parents ever since I’d stepped through the front door earlier. Situated a couple hours north of Los Angeles, the “retirement village,” as they called it, was immaculate. It resembled a glamorous apartment hotel with Spanish architecture, wide foyers and grounds that were landscaped with drought-tolerant plants for the California climate. As I was escorted to the lecture hall, I noticed a few residents peacefully walking dogs.

I took a second breath and began my answer. “My parents would love it here.” A hundred puzzled faces looked up at me, wondering what this comment about my parents had to do with the global energy economy. “When I talk with them about moving out of their burdensome three-bedroom home, they tell me that if they could just snap their fingers and be here right now,” I said, waving my arm high while making a grand snapping gesture, “they’d simply do it immediately. But, they find the idea of the transition utterly unbearable. So they’re stuck. Heels dug in, entrenched, immobile, paralyzed.”

While I was talking, an image popped, unwelcome, into my mind’s eye. I saw my parents’ fine china, stacked in a dusty credenza, untouched for 47-plus years. “They don’t want to go through their belongings and make choices,” I said. “They’re afraid of the amount of hard work.”

At this point I needed to pull away from my own emotions and check in with the people sitting in front of me. “Does any of this make sense to you? Does it seem familiar?” I saw a hundred white-haired heads nod simultaneously. I heard a hundred mumbled “Uh huhs.” In all my years of public speaking, this was the first time I’d experienced an entire room of people in agreement.

One gentleman near the front said, “That was me before I came here.” Another said, “I have some friends exactly like that right now.”

It’s easy for me to imagine a time off into the future, eventually, someday, where people will look back on all the credenzas and all the coal-fired power plants and regard them with the same quaint fondness that we have for Dick Van Dyke’s chimney sweep character from “Mary Poppins”: charming relics of a bygone era.

What I worry about, on both personal and global levels, is that it might take a catastrophic upheaval before the transition to better, cleaner, more comfortable conditions occurs. And those kinds of catastrophic events could be painful, personally and globally. I said as much to the group of seniors at the retirement village, and this time I didn’t need to ask them if they understood me. I could see it in their eyes. And the same guy in the front said quietly, “Yeah, that was me before I came here.”

Thank you for reading, and thank you for your comments.

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1954 Inspection Tour

In December 1954, only a few months after becoming the director of JPL, Dr. William Pickering (in the light-colored suit) hosted a visit by Frank H. Higgins, assistant secretary of the Army, and several members of his military entourage. At that time, JPL was under contract to Army Ordnance to develop guided missiles. In this photo, the group is gathered in the control room of the 20-inch wind tunnel. Frank Goddard (in the dark suit), chief of the Supersonic Aerodynamics Division, assisted with the tour and Bud Schurmeier, manager of the Wind Tunnel Section, observed from the back of the room while technicians conducted a demonstration.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.


  • Julie Cooper

Photograph of a landfill

We say we throw our trash away. But, where is 'away'?

Yesterday I was meeting with a few scientists down at the University of California, Irvine. Like any other campus, there were plenty of trash cans. Except they weren’t called trash cans. Some were labeled “recycling” and others were named “landfill.” It struck me how a simple shift in what we name something can make such a difference in how our mind sees it. Trash is a vague concept whereas landfill is a specific location with a concrete meaning and has an extremely different connotation from the word “trash.” If it’s trash, then we can say we’re “throwing it away.” Trash goes to that invisible place called “away.” If it’s landfill, then it goes in the, you know, landfill, the most unglamorous place of all.

Over the weekend a Mylar balloon landed in my yard. It reminded me of the idea of away. People like to release balloons into the sky as a celebration. The balloons are carried “away.” But the balloons don’t really go away. They don’t go anywhere; they stay here on Earth, sometimes in people’s yards, but most often balloons released into the sky end up in the ocean. This is why I’ve always hated balloons. To me, they represent society’s collective decision to not see how much we waste; to pay as little attention as possible to that place we’ve decided to label “away.”

Carbon pollution is one more of our “aways.”

We turn on the light to see, but all the wires that wind from the switch, through the wall, across town to the power plant that releases the colorless, odorless, heat-absorbing gas remain in the invisible realm of our “away.” We know it’s there because instruments such as NASA’s Atmospheric Infrared Sounder (AIRS) and Orbiting Carbon Observatory-2 (OCO-2) do see it. But carbon dioxide gas and the heat it traps aren’t going away, not any time soon, not until we start to change the way we see our world.

Because there is no such thing as “away.” The only thing that’s real is here.

Recycling and landfill bins.
Recycling and "landfill" bins on the campus of the University of California, Irvine.View larger image

I look forward to your comments.

Thank you,

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This view of Ceres shows some bright material that is not confined to “spots.”

Dear Descendawnts,

Flying on a blue-green ray of xenon ions, Dawn is gracefully descending toward dwarf planet Ceres. Even as Dawn prepares for a sumptuous new feast in its next mapping orbit, scientists are continuing to delight in the delicacies Ceres has already served. With a wonderfully rich bounty of pictures and other observations already secured, the explorer is now on its way to an even better vantage point.

Dawn Survey Orbit Image 31 This image, taken by NASA's Dawn spacecraft, shows dwarf planet Ceres from an altitude of 2,700 miles (4,400 kilometers). The image, with a resolution of 1,400 feet (410 meters) per pixel, was taken on June 25, 2015.
Dawn was in its second mapping orbit at an altitude of 2,700 miles (4,400 kilometers) when it took this picture of Ceres. This area shows relatively few craters, suggesting it is younger than some other areas on Ceres. Some bright spots are visible, although they are not as prominent as the most famous bright spots. Scientists do not yet have a clear explanation for them, but you can register your vote here. Click on the picture (or follow the link to the full image) for a better view of some interesting narrow, straight features in the lower left. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. Full image and caption

Dawn takes great advantage of its unique ion propulsion system to maneuver extensively in orbit, optimizing its views of the alien world that beckoned for more than two centuries before a terrestrial ambassador arrived in March. Dawn has been in powered flight for most of its time in space, gently thrusting with its ion engine for 69 percent of the time since it embarked on its bold interplanetary adventure in 2007. Such a flight profile is entirely different from the great majority of space missions. Most spacecraft coast most of the time (just as planets do), making only brief maneuvers that may add up to just a few hours or even less over the course of a mission of many years. But most spacecraft could not accomplish Dawn’s ambitious mission. Indeed, no other spacecraft could. The only ship ever to orbit two extraterrestrial destinations, Dawn accomplishes what would be impossible with conventional technology. With the extraordinary capability of ion propulsion, it is truly an interplanetary spaceship.

In addition to using its ion engine to travel to Vesta, enter into orbit around the protoplanet in 2011, break out of orbit in 2012, travel to Ceres and enter into orbit there this year, Dawn relies on the same system to fly to different orbits around these worlds it unveils, executing complex and graceful spirals around its gravitational master. After conducting wonderfully successful observation campaigns in its preantepenultimate Ceres orbit 8,400 miles (13,600 kilometers) high in April and May and its antepenultimate orbit at 2,700 miles (4,400 kilometers) in June, Dawn commenced its spiral descent to the penultimate orbit at 915 miles (1,470 kilometers) on June 30. (We will discuss this orbital altitude in more detail below.) A glitch interrupted the maneuvering almost as soon as it began, when protective software detected a discrepancy in the probe’s orientation. But thanks to the exceptional flexibility built into the plans, the mission could easily accommodate the change in schedule that followed. It will have no effect on the outcome of the exploration of Ceres. Let’s see what happened.

Survey orbit to HAMO
Dawn’s spiral descent from its second mapping orbit (survey), at 2,700 miles (4,400 kilometers), to its third (HAMO), at 915 miles (1,470 kilometers). The two mapping orbits are shown in green. The color of Dawn’s trajectory progresses through the spectrum from blue, when it began ion-thrusting in survey orbit, to red, when it arrives in HAMO. The red dashed sections show where Dawn is coasting for telecommunications. Compare this to the previous spiral. Image credit: NASA/JPL-Caltech

Control of Dawn’s orientation in the weightless conditions of spaceflight is the responsibility of the attitude control system. (To maintain a mystique about their work, engineers use the term “attitude” instead of “orientation.” This system also happens to have a very positive attitude about its work.) Dawn (and all other objects in three-dimensional space) can turn about three mutually perpendicular axes. The axes may be called pitch, roll and yaw; left/right, front/back and up/down; x, y and z; rock, paper and scissors; chocolate, vanilla and strawberry; Peter, Paul and Mary; etc., but whatever their names, attitude control has several different means to turn or to stabilize each axis. Earlier in its journey, the spacecraft depended on devices known as reaction wheels. As we have discussed in many Dawn Journals, that method is now used only rarely, because two of the four units have failed. The remaining two are being saved for the ultimate orbit at about 230 miles (375 kilometers), which Dawn will attain at the end of this year. Instead of reaction wheels, Dawn has been using its reaction control system, shooting puffs of hydrazine, a conventional rocket propellant, through small jets. (This is entirely different from the ion propulsion system, which expels high velocity xenon ions to change and control Dawn’s path through space. The reaction control system is used only to change and control attitude.)

Whenever Dawn is firing one of its three ion engines, its attitude control system uses still another method. The ship only operates one engine at a time, and attitude control swivels the mechanical gimbal system that holds that engine, thus imparting a small torque to the spacecraft, providing the means to control two axes (pitch and yaw, for example, or chocolate and strawberry). For the third axis (roll or vanilla), it still uses the hydrazine jets of the reaction control system.

On June 30, engine #3 came to life on schedule at 10:32:19 p.m. PDT to begin nearly five weeks of maneuvers. Attitude control deftly switched from using the reaction control system for all three axes to only one, and controlling the other two axes by tipping and tilting the engine with gimbal #3. But the control was not as effective as it should have been. Software monitoring the attitude recognized the condition but wisely avoided reacting too soon, instead giving attitude control time to try to rectify it. Nevertheless, the situation did not improve. Gradually the attitude deviated more and more from what it should have been, despite attitude control’s efforts. Seventeen minutes after thrusting started, the error had grown to 10 degrees. That’s comparable to how far the hour hand of a clock moves in 20 minutes, so Dawn was rotating only a little faster than an hour hand. But even that was more than the sophisticated probe could allow, so at 10:49:27 p.m., the main computer declared one of the “safe modes,” special configurations designed to protect the ship and the mission in uncertain, unexpected or difficult circumstances.

The spacecraft smoothly entered safe mode by turning off the ion engine, reconfiguring other systems, broadcasting a continuous radio signal through one of its antennas and then patiently awaiting further instructions. The radio transmission was received on a distant planet the next day. (It may yet be received on some other planets in the future, but we shall focus here on the response by Earthlings.) One of NASA’s Deep Space Network stations in Australia picked up the signal on July 1, and the mission control team at JPL began investigating immediately.

Engineers assessed the health of the spacecraft and soon started returning it to its normal configuration. By analyzing the myriad diagnostic details reported by the robot over the next few days, they determined that the gimbal mechanism had not operated correctly, so when attitude control tried to change the angle of the ion engine, it did not achieve the desired result.

Because Dawn had already accomplished more than 96 percent of the planned ion-thrusting for the entire mission (nearly 5.5 years so far), the remaining thrusting could easily be accomplished with only one of the ion engines. (Note that the 96 percent here is different from the 69 percent of the total time since launch mentioned above, simply because Dawn has been scheduled not to thrust some of the time, including when it takes data at Vesta and Ceres.) Similarly, of the ion propulsion system’s two computer controllers, two power units and two sets of valves and other plumbing for the xenon, the mission could be completed with only one of each. So although engineers likely could restore gimbal #3’s performance, they chose to switch to another gimbal (and thus another engine) and move on. Dawn’s goal is to explore a mysterious, fascinating world that used to be known as a planet, not to perform complex (and unnecessary) interplanetary gimbal repairs.

One of the benefits of being in orbit (besides it being an incredibly cool place to be) is that Dawn can linger at Ceres, studying it in great detail rather than being constrained by a fast flight and a quick glimpse. By the same principle, there was no urgency in resuming the spiral descent. The second mapping orbit was a perfectly fine place for the spacecraft, and it could circle Ceres there every 3.1 days as long as necessary. (Dawn consumed its hydrazine propellant at a very, very low rate while in that orbit, so the extra time there had a negligible cost, even as measured by the most precious resource.)

The operations team took the time to be cautious and to ensure that they understood the nature of the faulty gimbal well enough to be confident that the ship could continue its smooth sailing. They devised a test to confirm Dawn’s readiness to resume its spiral maneuvers. After swapping to gimbal #2 (and ipso facto engine #2), Dawn thrust from July 14 to 16 and demonstrated the excellent performance the operations team has seen so often from the veteran space traveler. Having passed its test with flying colors (or perhaps even with orbiting colors), Dawn is now well on its way to its third mapping orbit.

Artist’s concept of Dawn thrusting with ion engine #2.
Artist’s concept of Dawn thrusting with ion engine #2. The spacecraft captured the view of Ceres in June, and the intriguing cone described last month is visible on the limb at lower left. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. Background image and caption

The gradual descent from the second mapping orbit to the third will require 25 revolutions. The maneuvers will conclude in about two weeks. (As always, you can follow the progress with your correspondent’s frequent and succinct updates here.) As in each mapping orbit, following arrival, a few days will be required in order to prepare for a new round of intensive observations. That third observing campaign will begin on August 17 and last more than two months.

Although this is the second lowest of the mapping orbits, it is also known as the high altitude mapping orbit (HAMO) for mysterious historical reasons. We presented an overview of the HAMO plans last year. Next month, we will describe how the flight team has built on a number of successes since then to make the plans even better.

The view of the landscapes on this distant and exotic dwarf planet from the third mapping orbit will be fantastic. How can we be so sure? The view in the second mapping orbit was fantastic, and it will be three times sharper in the upcoming orbit. Quod erat demonstrandum! To see the sights at Ceres, go there or go here.

Part of the flexibility built into the plans was to measure Ceres’ gravity field as accurately as possible in each mapping orbit and use that knowledge to refine the design for the subsequent orbital phase. Thanks to the extensive gravity measurements in the second mapping orbit in June, navigators were able not only to plot a spiral course but also to calculate the parameters for the next orbit to provide the views needed for the complex mapping activities.

This color-coded map from NASA's Dawn mission shows the highs and lows of topography on the surface of dwarf planet Ceres. It is labeled with names of features approved by the International Astronomical Union.
This map of Ceres depicts the topography ranging from 4.7 miles (7.5 kilometers) low in indigo to 4.7 miles (7.5 kilometers) high in white. (As a technical detail, the topography is shown relative to an ellipsoid of dimensions very close to those in the paragraph below.) The names of features have been approved by the International Astronomical Union following the system described in December. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. Full image and caption

We have discussed some of the difficulty in describing the orbital altitude, including variations in the elevation of the terrain, just as a plane flying over mountains and valleys does not maintain a fixed altitude. As you might expect on a world battered by more than four billion years in the main asteroid belt and with its own internal geological forces, Ceres has its ups and downs. (The topographical map above displays them, and you can see a cool animation of Ceres showing off its topography here.) In addition to local topographical features, its overall shape is not perfectly spherical, as we discussed in May. Ongoing refinements based on Dawn’s measurements now indicate the average diameter is 584 miles (940 kilometers), but the equatorial diameter is 599 miles (964 kilometers), whereas the polar diameter is 556 miles (894 kilometers). Moreover, the orbits themselves are not perfect circles, and irregularities in the gravitational field, caused by regions of lower and higher density inside the dwarf planet, tug less or more on the craft, making it move up and down somewhat. (By using that same principle, scientists learn about the interior structure of Ceres and Vesta with very accurate measurements of the subtleties in the spacecraft’s orbital motions.) Although Dawn’s average altitude will be 915 miles (1,470 kilometers), its actual distance above the ground will vary over a range of about 25 miles (40 kilometers).

In March we summarized the four Ceres mapping orbits along with a guarantee that the dates would change. In addition to delivering exciting interplanetary adventures to thrill anyone who has ever gazed at the night sky in wonder, Dawn delivers on its promises. Therefore, we present the updated table here. With such a long and complex mission taking place in orbit around the largest previously uncharted world in the inner solar system, further changes are highly likely. (Nevertheless, we would consider the probability to be low that changes will occur for the phases in the past.)

Table showing Dawn's activities during the various mapping orbits
Find out more about Dawn's activities during these mapping orbits: RC3, survey, HAMO, LAMO

Click on the name of each orbit for a more detailed description. As a reminder, the last column illustrates how large Ceres appears to be from Dawn’s perspective by comparing it with a view of a soccer ball. (Note that Ceres is not only 4.4 million times the diameter of a soccer ball but it is a lot more fun to play with.)

Resolute and resilient, Dawn patiently continues its graceful spirals, propelled not only by its ion engine but also by the passions of everyone who yearns for new knowledge and noble adventures. Humankind’s robotic emissary is well on its way to providing more fascinating insights for everyone who longs to know the cosmos.

Dawn is 1,500 miles (2,400 kilometers) from Ceres. It is also 1.95 AU (181 million miles, or 291 million kilometers) from Earth, or 785 times as far as the moon and 1.92 times as far as the sun today. Radio signals, traveling at the universal limit of the speed of light, take 32 minutes to make the round trip.

Dr. Marc D. Rayman
8:00 p.m. PDT July 29, 2015

› Learn more about the Dawn mission


  • Marc Rayman

Ed Begley Jr. inspects his oak hardwood flooring

Ed chats with John Ezqueda from All Valley Solar

Ed standing outside the construction site of his new home.

Ed Begley Jr. was one of the first people I met when I moved from Hong Kong to Los Angeles in the mid ‘90s, so when we sat down this week to talk about environmentalism and the new ultra-green home he’s building, I knew exactly what direction I wanted to take our conversation. I wanted to find out what made Begley different from almost every other person I’ve met. I wanted to find out what made him so completely dedicated to a green lifestyle.

A lot of people pay lip service to going green, or take a handful of actions to reduce their impact on the environment, or complain about others who should do more or go as far as a low-carbon lifestyle, but I don’t think I’ve ever met anyone who’s made more of a concerted commitment to being green as Ed has. I wanted know: What was that thing that made him do it, that impetus that really got him to push through where so many others just don’t?

Begley started by explaining how he learned to be frugal from his father, Ed Begley Sr., who “was not a star, he was a working actor like I am,” even though he won an Academy Award. He told me his father was the son of Irish immigrants, lived through the Great Depression and was a factory worker who found career success as an actor later in life. “We turned off the lights, we turned off the water.” But I brushed off that explanation. Loads of people get stuck with (oops, I meant are fortunate enough to have) a thrifty father. If thriftiness were all it took, everyone would have gone green, like, forever ago.

Then he described growing up in the 1950s in Los Angeles. “When I was five or six, it hurt to breathe in the Valley. That’s the way it was in the '50s. We kids were running around playing tag and some days you’d just be sitting and you’d have trouble breathing. Burbank was crazy smoggy,” he continued, “because of the big electric power plant that burned dirty fuel. We’re in the middle of San Fernando Valley, yet you can’t see the mountains.” Instead of complaining, Ed said, “My dad would ask me: ‘What are you for? What would you do to fix it?’ He was a can-do guy.” Seeing the air quality improve taught Begley that he could do something, it taught him to have hope for a cleaner environment.

This point of view is very different from my own and from that of the current generations who can barely remember anything but news of political gridlock and constant bickering over climate science, climate change denial, and whether or not humans are to blame. It’s hard for most of us under 60 to remember a time when we felt like each of us, as individuals within our greater society, could make a difference, but Begley grew up with a deep inner belief that his actions could have impact. “Corporations, government, individuals: you need all three legs for the stool to stay steady,” he said. “We’re not waiting on government or corporations to do something on climate, we’re going to do it.”

Lifestyles of the Rich and Anxious

Another factor that helped shape his choices was his experience with rich and famous celebrities. “We would visit some of these people with fat houses and they didn’t seem one bit happier to me; in fact, they had all this stress and all these problems.” Ed saw what happened to people who were wealthy enough to buy lots and lots of material things. “I met all these movie stars and saw the anxiety that came with more stuff.”

Everything we buy, everything we own has a carbon footprint. More than just the purchase price, our things have a cost to the environment. The more possessions we have, the greater the environmental impact. The problem is, though, it’s really hard to tell people they should buy fewer possessions, especially when we’re constantly told we would be happier with more. Well, Ed spent his time with some super famous and super rich actors who actually had all that more. He observed extreme wealth, saw that more stuff didn’t make his friends happier and learned that, beyond meeting your basic needs, more and more material possessions only made his friends unhappier, and that deeply affected him. It influenced the way he decided to live and what he was willing to spend monetarily or expend environmentally.

Actions Are Louder Than Words

But perhaps the most interesting thing I found out about Ed during our chat was that he’s a natural science wonk. Who knew? I’d asked him to tell me about his transition from kid/teen/young man who thought he could make a difference to knowing that he’d become a real leader in the environmental movement. He told me a story about going on a bus caravan that went around California in 1986 with Jane Fonda and a bunch of other Hollywood people to rally students about a consumer right-to-know bill. “I had a keen interest in science,” he told me, “so it turns out I knew about PCBs [polychlorinated biphenyls] and hexavalent chromium and trichloroethylene. I had read up on these things and the knowledge gave me the ease to speak well about it. So all of a sudden all the microphones were pointed at me.” He hadn’t planned it; he had merely been interested enough in the topic to be knowledgeable about the details. “I like nuts and bolts. I’m definitely a gear-head. That’s why I love my electric car. I want to know: How many amps does this draw, how many watts is this charger?”

As he spoke, Ed paused to check his phone. “It’s Harry Dean Stanton, he just called. I help him with a crossword puzzle every day. I have the answers right here printed on post consumer recycled paper.” He pulled a piece of folded paper out of his pocket, showed it to me, then put it back and continued talking. “I didn’t like my chemistry set, I loved it. I loved my Erector Set for years.” I noticed he was focused on specifics. Details fascinate him. He could prattle on endlessly about high storage capacity batteries, or solar array voltage, or bathroom and kitchen tiles fabricated with recycled material. It occurred to me that his house is just one giant, green Erector Set.

Still, I pressed him to try to find out what made him the greenest guy around. “I just did it cause I knew it was right,” he said. “I rode my bike to the Vanity Fair big Oscars party in the ‘90s, and I was just trying to quietly and surreptitiously lock the bike up when suddenly all these paparazzi descended on me. They took all these pictures and I was a superstar. If you do something silently and deliberately people notice.”

Clearly people have noticed. So the purpose of doing this green house is to demonstrate that both electrical and water conservation efforts can be done. “If I could do it, anybody could do it,” Ed said.

You can follow Ed on Twitter @edbegleyjr.

As always, I look forward to your comments.

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