This composite of 30 images of asteroid 2014 JO25 was generated with radar data collected using NASA’s Goldstone Solar System Radar in California’s Mojave Desert on Tuesday April 18. Credit: NASA/JPL-Caltech/GSSR
Asteroid 2014 JO25, discovered in 2014 by the Catalina Sky Survey in Arizona, was in the spotlight today (April 19) when it flew by Earth at just four times the distance of the Moon. Today’s encounter is the closest the object has come to the Earth in 400 years and will be its closest approach for at least the next 500 years.
Lots of asteroids zip by our planet, and new ones are discovered every week. What makes 2014 JO25 different it’s one of nearly 1,800 PHAs (Potentially Hazardous Asteroids) that are big enough and occasionally pass close enough to Earth to be of concern. PHAs have diameters of at least 100-150 meters (330-490 feet) and pass less than 0.05 a.u (7.5 million km / 4.6 million miles) from our planet. Good thing for earthlings, no known PHA is predicted to impact Earth for at least the next 100 years.
Most of these Earth-approachers are on the small side, only a few to a few dozen meters (yards) across. 2014 JO25 was originally estimated at ~2,000 feet wide, but thanks to radar observations made the past couple days, we now know it’s nearly twice that size. Radar images of asteroid were made early this morning with NASA’s 230-foot (70-meter) radio antenna at Goldstone Deep Space Communications Complex in California. They reveal a peanut-shaped asteroid that rotates about once every 5 hours and show details as small as 25 feet.
NASA radar images and animation of asteroid 2015 JO25
The larger of the two lobes is about 2,000 feet (620 meters) across, making the total length closer to 4,000 feet. That’s similar in size (though not as long) as the Rock of Gibraltar that stands at the southwestern tip of Europe at the tip of the Iberian Peninsula.
“The asteroid has a contact binary structure — two lobes connected by a neck-like region,” said Shantanu Naidu, a scientist from NASA’s Jet Propulsion Laboratory in Pasadena, California, who led the Goldstone observations. “The images show flat facets, concavities and angular topography.” Contact binaries form when two separate asteroids come close enough together to touch and meld as one.
The Goldstone dish dish, based in the Mojave Desert near Barstow, Cal. is used for radar mapping of planets, comets, asteroids and the Moon. Credit: NASA
Radar observations of the asteroid have also been underway at the National Science Foundation’s Arecibo Observatory in Puerto Rico with more observations coming today through the 21st which may show even finer details. The technique of pinging asteroids with radio waves and eking out information based on the returning echoes has been used to observe hundreds of asteroids.
When these relics from the early solar system pass relatively close to Earth, astronomers can glean their sizes, shapes, rotation, surface features, and roughness, as well as determine their orbits with precision.
Because of 2014 JO25’s relatively large size and proximity, it’s bright enough to spot in a small telescope this evening. It will shine around magnitude +10.9 from North America tonight as it travels south-southwest across the dim constellation Coma Berenices behind the tail of Leo the Lion. A good map and 3-inch or larger telescope should show it.
Use the maps at this link to help you find and track the asteroid tonight. The key to spotting it is to allow time to identify and get familiar with the star field the asteroid will pass through 10 to 15 minutes in advance — then lay in wait for the moving object. Don’t be surprised if 2014 JO25 deviates a little from the predicted path depending on your location and late changes to its orbit, so keep watch not only on the path but around it, too. Good luck!
This composite of 25 images of asteroid 2017 BQ6 was generated with radar data collected using NASA’s Goldstone Solar System Radar in California’s Mojave Desert. It sped by Earth on Feb. 7 at a speed of around 25,560 mph (7.1 km/s) relative to the planet. The images have resolutions as fine as 12 feet (3.75 meters) per pixel. Credit: NASA/JPL-Caltech/GSSR
To radar imager Lance Benner at JPL in Pasadena, asteroid 2017 BQ6 resembles the polygonal dice used in Dungeons and Dragons. But my eyes see something closer to a stepping stone or paver you’d use to build a walkway. However you picture it, this asteroid is more angular than most imaged by radar.
It flew harmlessly by Earth on Feb. 7 at 1:36 a.m. EST (6:36 UT) at about 6.6 times the distance between Earth and the moon or some about 1.6 million miles. Based on 2017 BQ6’s brightness, astronomers estimate the hurtling boulder about 660 feet (200 meters) across. The recent flyby made for a perfect opportunity to bounce radio waves off the object, harvest their echoes and build an image of giant space boulder no one had ever seen close up before.
NASA’s 70-meter antennas are the largest and most sensitive Deep Sky Network antennas, capable of tracking a spacecraft traveling tens of billions of miles from Earth. This one at Goldstone not only tracked Voyager 2’s Neptune encounter, it also received Neil Armstrong’s famous communication from Apollo 11: “That’s one small step for a man. One giant leap for mankind.” Credit: JPL-Caltech/GSSR
The images of the asteroid were obtained on Feb. 6 and 7 with NASA’s 230-foot (70-meter) antenna at the Goldstone Deep Space Communications Complex in California and reveal an irregular, angular-appearing asteroid:
Animation of 2017 BQ6. The near-Earth asteroid has a rotation period of about 3 hours. Credit: NASA/JPL-Caltech/GSSR
“The radar images show relatively sharp corners, flat regions, concavities, and small bright spots that may be boulders,” said Lance Benner of NASA’s Jet Propulsion Laboratory in Pasadena, California, who leads the agency’s asteroid radar research program. “Asteroid 2017 BQ6 reminds me of the dice used when playing Dungeons and Dragons.”
Radar has been used to observe hundreds of asteroids. Even through very large telescopes, 2017 BQ6 would have appeared exactly like a star, but the radar technique reveals shape, size, rotation, roughness and even surface features.
This chart shows how data from NASA’s Wide-field Infrared Survey Explorer, or WISE, has led to revisions in the estimated population of near-Earth asteroids. Credit: NASA/JPL-Caltech
To create the images, Benner conducted a controlled experiment on the asteroid, transmitting a signal with well-known characteristics to the object and then, by comparing the echo to the transmission, deduced its properties. According to NASA’s Asteroid Radar Research site, measuring how the echo power spreads out over time along with changes in its frequency caused by the Doppler Effect (object approaching or receding from Earth), provide the data to construct two-dimensional images with resolutions finer than 33 feet (10 meters) if the echoes are strong enough.
This orbital diagram shows the close approach of 2017 BQ6 to Earth on Feb. 7, 2017. Credit: NASA/JPL Horizons
In late October 2016, the number of known near-Earth asteroids topped 15,000 with new discoveries averaging about 30 a week. A near-Earth asteroid is defined as a rocky body that approaches within approximately 1.3 times Earth’s average distance to the Sun. This distance then brings the asteroid within roughly 30 million miles (50 million km) of Earth’s orbit. To date, astronomers have already discovered more than 90% of the estimated number of the large near-Earth objects or those larger than 0.6 miles (1 km). It’s estimated that more than a million NEAs smaller than 330 feet (100 meters) lurk in the void. Time to get crackin’.
These radar images of comet P/2016 BA14 were taken on March 23, 2016, by scientists using an antenna of NASA's Deep Space Network at Goldstone, California. At the time, the comet was about 2.2 million miles (3.5 million kilometers) from Earth. Credit: NASA/JPL-Caltech/GSSR
These radar images of comet P/2016 BA14 were taken on March 23, 2016, by scientists using an antenna of NASA’s Deep Space Network at Goldstone, California. At the time, the comet was about 2.2 million miles (3.5 million kilometers) from Earth. Credit: NASA/JPL-Caltech/GSSR
On March 22, Comet P/2016 BA14 (Pan-STARRS) flew just 2.2 million miles (3.5 million kilometers) from Earth, making it the third closest comet ever recorded. The last time a comet appeared on our doorstep was in 1770, when Lexell’s Comet breezed by at about half that distance. Through a telescope, comet BA14 looked (and still looks) like a faint star, though time exposures reveal a short, weak tail. With an excellent map and large amateur telescope you might still find it making a bead across the Big Dipper and constellation Bootes tonight through the weekend.
Flyby Comet Imaged by Radar
While normal telescopes show few details, NASA’s Goldstone Solar System Radar in California’s Mojave Desert pinged P/2016 BA14 with radar over three nights during closest approach and created a series of crisp, detailed images from the returning echoes. They show a bigger comet than expected — about 3,000 feet (one kilometer) across — and resolve features as small as 26 feet (8 meters) across.
“The radar images show that the comet has an irregular shape: looks like a brick on one side and a pear on the other,” said Shantanu Naidu, a researcher at NASA’s Jet Propulsion Laboratory. “We can see quite a few signatures related to topographic features such as large flat regions, small concavities and ridges on the surface of the nucleus.”
I honestly thought we’d see a more irregular shape assuming that astronomers were correct in thinking that BA14 broke off from its parent 252P/LINEAR though it’s possible it happened so long ago that the “damage” has been repaired by vaporizing ice softening its contours.
Comets are as dark as charcoal but appear light only because the sun illuminates them against the blackness of outer space. I shone a flashlight on a charcoal briquette (left) to simulate comet lighting. The same charcoal when viewed in normal light appears black. Credit: Bob King
Radar also shows that the comet is rotating on its axis once every 35 to 40 hours. While radar eyes focused on BA14, Vishnu Reddy, of the Planetary Science Institute, Tucson, Arizona, used the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii to examine the comet in infrared light. He discovered its dark surface reflects less than 3% of the sunlight that falls on it. The infrared data is expected to yield clues of the comet’s composition as well.
Illustration of Comet 67P/Churyumov-Gerasimenko brought down to Earth in the city of Los Angeles, Calif. Not only can we appreciate its size but also its truly dark surface. Credit: ESA and anosmicovni
Comets are exceptionally dark objects often compared to the appearance of a fresh asphalt road or parking lot. They appear bright in photos because seen against the blackness of space, they’re still reflective enough to stand out. Comet 67P/Churyumov-Gerasimenko, still the apple of the orbiter Rosetta’s eye, is similarly dark, reflecting about 4% of sunlight.
What makes comets so dark even though they composed primarily of ice? Astronomers believe a comet grows a dark ‘skin’ both from accumulated dust and irradiation of its pristine ices by cosmic rays. Cosmic rays loosen oxygen atoms from water ice, freeing them to combine with simple carbon molecules present on comets to form larger, more complex and darker compounds resembling tars and crude oil. Dust settles on a comet’s surface after it’s set free from ice that vaporizes in sunlight.
What a view! Comet 67P/C-G photographed from a distance of just 7.5 miles (12 kilometers) on March 19, 2016 by Rosetta’s Navcam. The largest boulder to the right is Cheops, which stands about 82 feet (25 meters) high. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
I live in Minnesota, where our annual State Fair features every kind of deep-fried food you can imagine: deep-fried Twinkies, deep-fried fruit, deep-fried bacon and even deep-fried Smores. Just now, I can’t shake the thought that comets are just another deep-fried confection made of pristine, 4.5-billion-year-old ice toasted by eons of sunlight and cosmic bombardment.
Individual radar images of 2004 BL86 and its moon. The asteroid appears very lumpy, possibly from unresolved crater rims. The moon appears elongated but that may be an artifact and not its true shape. Credit: NASA
New video of 2004 BL86 and its moon
Newly processed images of asteroid 2004 BL86 made during its brush with Earth Monday night reveal fresh details of its lumpy surface and orbiting moon. We’ve learned from both optical and radar data that Alpha, the main body, spins once every 2.6 hours. Beta (the moon) spins more slowly.
The images were made by bouncing radio waves off the surface of the bodies using NASA’s 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, Calif. Radar “pinging” reveals information about the shape, velocity, rotation rate and surface features of close-approaching asteroids. But the resulting images can be confusing to interpret. Why? Because they’re not really photos as we know it.
For one, the moon appears to be revolving perpendicular to the main body which would be very unusual. Most moons orbit their primary approximately in the plane of its equator like Earth’s moon and Jupiter’s four Galilean moons. That’s almost certainly the case with Beta. Radar imagery is assembled from echoes or radio signals returned from the asteroid after bouncing off its surface. Unlike an optical image, we see the asteroid by reflected pulses of radio energy beamed from the antenna. To interpret them, we’ll need to put on our radar glasses.
Bright areas don’t necessarily appear bright to the eye because radar sees the world differently. Metallic asteroids appear much brighter than stony types; rougher surfaces also look brighter than smooth ones. In a sense these aren’t pictures at all but graphs of the radar pulse’s time delay, Doppler shift and intensity that have been converted into an image.
Another set of images of 2004 BL86 and its moon. Credit: NAIC Observatory / Arecibo Observatory
In the images above, the left to right direction or x-axis in the photo plots the toward and away motion or Doppler shift of the asteroid. You’ll recall that light from an object approaching Earth gets bunched up into shorter wavelengths or blue-shifted compared to red-shifted light given off by an object moving away from Earth. A more rapidly rotating object will appear larger than one spinning slowly. The moon appears elongated probably because it’s rotating more slowly than the Alpha primary.
Meanwhile, the up and down direction or y-axis in the images shows the time delay in the reflected radar pulse on its return trip to the transmitter. Movement up and down indicates a change in 2004 BL86’s distance from the transmitter, and movement left to right indicates rotation. Brightness variations depend on the strength of the returned signal with more radar-reflective areas appearing brighter. The moon appears quite bright because – assuming it’s rotating more slowly – the total signal strength is concentrated in one small area compared to being spread out by the faster-spinning main body.
If that’s not enough to wrap your brain around, consider that any particular point in the image maps to multiple points on the real asteroid. That means no matter how oddly shaped 2004 BL86 is in real life, it appears round or oval in radar images. Only multiple observations over time can help us learn the true shape of the asteroid.
You’ll often notice that radar images of asteroids appear to be lighted from directly above or below. The brighter edge indicates the radar pulse is returning from the leading edge of the object, the region closest to the dish. The further down you go in the image, the farther away that part of the asteroid is from the radar and the darker it appears.
Imagine for a moment an asteroid that’s either not rotating or rotating with one of its poles pointed exactly toward Earth. In radar images it would appear as a vertical line!
If you’re curious to learn more about the nature of radar images, here are two great resources:
Goldstone delay-Doppler images of 2014 SC324 obtained on October 25. The images span an interval of about 45 minutes and show considerable rotation
by this object, which has an irregular and elongated shape. Credit: NASA/JPL
Looks like we dodged a bullet. A bullet-shaped asteroid that is. The 70-meter Goldstone radar dish, part of NASA’s Deep Space Network, grabbed a collage of photos of Earth-approaching asteroid 2014 SC324 during its close flyby last Friday October 24. These are the first-ever photos of the space rock which was discovered September 30 this year by the Mt. Lemmon Survey. The level of detail is amazing considering that the object is only about 197 feet (60-meters) across. You can also see how incredibly fast it’s rotating – about 30-45 minutes for a one spin.
A cropped version of the photo to more clearly see the asteroid’s shape. 2014 SC324 passed just 1.5 lunar distances from Earth last week. Credit: NASA/JPL
In the cropped version, the shape is somewhat clearer with the asteroid appearing some four times longer than wide. 2014 SC324 belongs to the Apollo asteroid class, named for 1862 Apollo discovered in 1932 by German astronomer Karl Reinmuth. Apollo asteroids follow orbits that occasionally cross that of Earth’s, making them a potential threat to our planet. The famed February 15, 2013 Chelyabinsk fireball, with an approximate pre-atmospheric entry size of 59 feet (18-m), belonged to the Apollo class.
Three classes of asteroids that pass near Earth or cross its orbit are named for the first member discovered — Apollo, Aten and Amor. Apollo asteroids like 2014 SC324 routinely cross Earth’s orbit, Atens also cross but have different orbital characteristics and Amors cross Mars’ orbit but miss Earth’s. Credit: ESA
Lance Benner and colleagues at Goldstone also imaged another Apollo asteroid that passed through our neighborhood on October 19 called 2014 SM143. This larger object, estimated at around 650 feet (200-m) across, was discovered with the Pan-STARRS 1 telescope on Mt. Haleakala in Hawaii on September 17. Tell me we’re not some shiny ball on a solar system-sized pool table where the players fortunately miss their shot … most of the time.
Radar delay-Doppler images of asteroid 2014 HQ124. The Earth and radar transmitter are toward the top of each frame. Each frame has the same orientation, delay-Doppler dimensions, resolution (3.75 m by 0.0125 Hz), and duration (10 minutes). Arecibo images appear on the top row and Goldstone images appear on the other rows: Arecibo Observatory capabilities eliminated the "snow" visible in the other images.There is a gap of about 35 minutes between rows 1 and 2. Credit: Marina Brozovic and Joseph Jao, Jet Propulsion Laboratory/ Caltech/ NASA/ USRA/ Arecibo Observatory/ NSF
On June 8, the 370-meter (about 1,300-ft.) asteroid 2014 HQ124 breezed by Earth at a distance of just 800,000 miles (1.3 million km). Only hours after closest approach, astronomers used a pair of radio telescopes to produce some of the most detailed images of a near-Earth asteroid ever obtained. They reveal a peanut-shaped world called a ‘contact binary’, an asteroid comprised of two smaller bodies touching.
About one in six asteroids in the near-Earth population has this type of elongated or “peanut” shape. It’s thought that contact binaries form when two or more asteroids get close enough to touch and ‘stick’ together through their mutual gravitational attraction. Asteroid 25143 Itokawa, visited and sampled by the Japanese spacecraft Hayabusa in 2005, is another member of this shapely group.
Radar observations of asteroid 2014 HQ124 seen here in video
The 21 radar images were taken over a span of four hours and reveal a rotation rate of about 20 hours. They also show features as small as about 12 feet (3.75 meters) wide. This is the highest resolution currently possible using scientific radar antennas to produce images. Such sharp views were made possible for this asteroid by linking together two giant radio telescopes to enhance their capabilities.
Astronomers used the 230-foot (70-meter) Deep Space Network antenna at Goldstone, Calif. to beam radar signals at the asteroid which reflected them back to the much larger 1000-foot (305-meter) Arecibo dish in Puerto Rico. The technique greatly increases the amount of detail visible in radar images.
Aerial view of the 1,000-foot dish at Arecibo Observatory. Credit: NOAA
Arecibo Observatory and Goldstone radar facilities are unique for their ability to resolve features on asteroids, while most optical telescopes on the ground would see these cosmic neighbors simply as unresolved points of light. The radar images reveal a host of interesting features, including a large depression on the larger lobe as well as two blocky, sharp-edged features at the bottom on the radar echo (crater wall?) and a small protrusion along its long side that looks like a mountain. Scientists suspect that some of the bright features visible in multiple frames could be surface boulders.
“These radar observations show that the asteroid is a beauty, not a beast”, said Alessondra Springmann, a data analyst at Arecibo Observatory.
A single radar image frame close-up view of 2014 HQ124. Credit: NASA
The first five images in the sequence (top row in the montage) represent the data collected by Arecibo, and demonstrate that these data are 30 times brighter than what Goldstone can produce observing on its own. There’s a gap of about 35 minutes between the first and second rows in the montage, representing the time needed to switch from receiving at Arecibo to receiving at the smaller Goldstone station.
If you relish up-close images of asteroids as much as I do, check out NASA’s Asteroid Radar Research site for more photos and information on how radar pictures are made.
The participants of the DSN NASA Social gathered in front of the DSS-14 70-meter antenna at Goldstone, April 2, 2014.
When you’re talking to spacecraft billions of miles away, you need a powerful voice. And when you’re listening for their faint replies from those same staggering distances, you need an even bigger set of ears. Fortunately, NASA’s Deep Space Network has both — and last week I had the chance to see some of them up close and in person as one of the lucky participants in a NASA Social! Here’s my overview of what happened on those two exciting days.
(And if this doesn’t make you want to apply for the next Social, I don’t know what will.)
The main building at Jet Propulsion Laboratory in Pasadena (J. Major)
The event began on April 1 (no foolin’) at NASA’s Jet Propulsion Laboratory in Pasadena. Nestled at the feet of steep pine-covered hills northeast of Los Angeles, JPL’s campus is absolutely gorgeous… not quite the location you might imagine for the birthplace of robotic interplanetary explorers! But for over 55 years JPL has been developing some of the world’s most advanced spacecraft, from the Ranger probes which took NASA’s first close-up images of the Moon to the twin Voyagers that toured the Solar System’s outer planets, countless Earth-observing satellites that have revolutionized our ability to monitor global weather, and all of the rovers that have been our first “wheels on the ground” on Mars.
Of course, none of those missions would have been possible if we didn’t have the ability to communicate with the spacecraft. That’s why NASA’s Deep Space Network is such an integral — even if not oft-publicized — part of each and every mission… and has been for 50 years.
In fact, that was the purpose of this Social event which gathered together 50 space fans from across the U.S. — to celebrate the achievements of the DSN with an eye-opening tour of both JPL and the DSN’s Goldstone facility with its flagship 70-meter dish, located amongst the rocky scrub-covered hills in the middle of a military base in California’s Mojave desert.
For many participants — including myself — it was the first time visiting JPL. I can’t tell you how many times I’ve written about the news that comes out of it, featured its amazing images, and typed the credit line “NASA/JPL-Caltech” in the caption of a picture, so for me it was incredible to actually be there in person. Just driving through the front gate at JPL, with “Welcome To Our Universe” mounted over the window of the guard station, was mind-blowing!
Setting up camp in Mission Control (J. Major)This 16-inch-wide plaque is set into the floor of the “dark room” at JPL Mission Control, covered by a pane of clear acrylic. (J. Major)
From the Visitor’s Center we were gathered into groups and taken into the heart of JPL to get a look at the Mission Control room, aka the “center of the universe.” This is where all the data from ongoing space exploration missions arrives (after being collected by the Deep Space Network, of course.) And we didn’t just get to see Mission Control — we actually set up our computers there and got to take our seats at the very same desks that top JPL and NASA engineers and scientists used during the MSL landing in August 2012! In fact we were treated to a replay of Curiosity’s landing on the screens against the wall that first displayed the rover’s images of Gale Crater. The whole experience was a bit surreal — I vividly recall watching it live, and there we were in the same room as if it were happening all over again! (We even got to re-enact the celebration of the touchdown announcement as our group photo.)
After several presentations and Q&A sessions with NASA mission engineers — recorded live for NASA TV — we all embarked on a tour of JPL’s rock-strewn “Mars Yard” where a stunt double of Curiosity, named “Maggie,” resides in a super high-tech garage. Maggie helps engineers determine what Curiosity can and can’t do on Mars… much more safely than actually having the “real” rover attempt itself.
Watch the NASA TV coverage from Mission Control below:
The group then got the chance to see an actual spacecraft being built in the Spacecraft Assembly Facility, a huge clean room where engineers were building components of the upcoming SMAP (Soil Moisture Active Passive) satellite. Slated for launch in October, SMAP will take measurements of the planet’s soil moisture in its freeze/thaw states from orbit over a period of three years. As we watched from the windowed viewing platform several “bunny-suited” engineers were busy working on SMAP’s 6-meter reflector. In another six months or so the parts that were scattered around that clean room will be performing science in orbit!
Where space explorers are born: JPL’s Spacecraft Assembly Facility (J. Major)Randii Wessen (left) and Todd Barber (right) demonstrate… well, I’m not sure what they were demonstrating but it was very entertaining! (J. Major)
From there it was off to the JPL museum and some intimate (and highly animated!) discussions about mission technology with project formulator Randii Wessen and propulsion engineer Todd Barber. Afterward I took the opportunity to talk with Todd a bit about his role on the Cassini mission, for which he’s the lead propulsion engineer.
(You all know how much I adore Cassini, so that was a real treat.)
When we got back to Mission Control we had a chance to meet with and have photos taken with JPL’s very own “Mohawk guy” Bobak Ferdowsi, who achieved widespread fame during the internet broadcast landing of Curiosity. I had Bobak sign my toy Curiosity rover, which now has a “BF” on the back of its die-cast RTG. One for the space shelf!
The second half of the Social began early the next day — for me, very early. After getting up at 3:15 a.m. and making a two-hour drive from Pasadena to Barstow in the dark, I and the other participants met up with the Social bus in a park-and-ride lot at 6:00 just as the Sun was beginning to brighten the eastern sky. (Some had stayed overnight in Barstow, while others made the early drive out like I did.) Once the bus filled, we headed north into the Mojave to arrive at NASA’s Deep Space Network Communications Complex at Goldstone, located within the Fort Irwin military training area.
The 70-meter dish at NASA’s DSN complex at Goldstone (J. Major)
The location is rugged and remote — the perfect place to listen for the faint signals from spacecraft trundling across dusty Mars and soaring through the farthest reaches of the Solar System! The nine main DSN antennas at Goldstone are scattered across several square miles of desert, enormous dishes pointed more-or-less directly upward, aiming at the locations of distant spacecraft in order to both receive and transmit data. All of them are huge, but by far the most impressive is the gigantic 70-meter DSS-14 dish that towers above the rest in both height and width.
Recently renovated , the fully-positionable DSS-14 “Mars antenna” dish (so called because of its first mission tracking the Mariner 4 spacecraft in 1965) weighs in at 2.7 million kilograms yet “floats” atop a thin film of oil a quarter of a millimeter thick!
How smoothly does a three-thousand-ton radar dish move? We got to find out — check out the video below:
(Note: as it turned out, DSS-14 wasn’t turning to communicate with anything… the show was just for us!)
Of course, we all spent plenty of time taking pictures of the 70-meter, both inside and out — we were treated to a tour of this and several other dish sites hosted by JPL’s Jeff Osman, a specialist in the DSN antennas and their operations.
(One of us even chose to record the DSS-14 antenna with pencils and paper — watch fellow Social participant Jedediah Dore’s sketch and account of the experience here.)
Jim Erickson, JPL’s Project Manager for the Mars Rovers and MRO, speaks during the 50th Anniversary Event (J. Major)
The highlight of the day at Goldstone was (if not just being there!) was being present for the official celebration of the facility’s 50th anniversary. Featuring speakers from JPL and DSN, as well as many esteemed guests, the event — held indoors because of strong winds outside — commemorated the impact and important contributions of the complex over the past half-century of space exploration. According to speaker Jim Erickson of JPL, “There hasn’t been a time in my career when the DSN wasn’t there for us.”
After that the NASA Social group was invited to take a few moments to mingle with speakers and guests — when else would I have a chance to chat with JPL director Dr. Charles Elachi? — and then we all returned to our own meeting room where refreshments were waiting and a (quite delicious) DSN50 cake was cut and served.
It was truly a fantastic and well-planned event, giving 50 people the chance to see an integral part of our space program that, although it doesn’t usually receive the same kind of exposure that rocket launches and planetary landings enjoy, makes all of it possible.
Here’s to 50 more years of DSN and its long-distance relationship with all of our intrepid space explorers!
__________________
See what communications are currently coming in and going out of the DSN dishes — in Goldstone as well as in Madrid and Canberra — here, and learn more about the history of Goldstone here.
And a big thanks to Courtney O’Connor, Veronica McGregor, John Yembrick, and Stephanie Smith for putting this NASA Social together, Annie Wynn and Shannon Moore for setting up and organizing participant groups on Facebook and Google (which makes offsite planning so much easier), Jeff Osman and Shannon McConnell for the tours of the DSN sites and, of course, everyone at JPL and Goldstone who helped to make the event a wonderful success!
Would you like to be a part of a NASA Social? Find out what events are coming up and how to apply for them here.
These radar images of asteroid 2013 ET were obtained when the asteroid was about 693,000 miles from Earth. The images span 1.3 hours or about 1/3 or the asteroid's rotation rate. Click to enlarge. Credit: NASA/JPL-Caltech/GSSR
Another space rock sat pretty for NASA’s big dish photographer. The 70-meter (230-feet) Goldstone antenna zinged radio waves at 2013 ET on March 10 when the asteroid flew by Earth at 2.9 lunar distances or about 693,000 miles (1.1 million km).
By studying the returned echoes, astronomers pieced together 18 images of a rugged, irregular-shaped object about 130 feet (40 m) across. Radar measurements of an asteroid’s distance and speed nail down its orbit with great accuracy, enabling scientists to predict whether or not it might become a danger to the planet at a future date.
The Goldstone dish dish, based in the Mojave Desert near Barstow, Cal. is used for radar mapping of planets, comets, asteroids and the moon. Credit: NASA
It’s also the only way outside of a sending a spacecraft to the object of seeing a small asteroid’s shape and surface features. Most optical telescopes cannot resolve asteroids as anything more than points of light.
By convention, radar images appear “lit” from above. That’s the side closest to the antenna. As you examine a radar image from top to bottom, distance from the antenna increases and the asteroid fades. If the equator of the asteroid faces the antenna, it will appear brightly illuminated at the top of the image. If the antenna faces one of the poles, the pole will be on top and lit up. It takes a bit of getting used to.
Nine radar images of near-Earth asteroid 2007 PA8 obtained between by NASA’s 230-foot-wide (70-meter) Deep Space Network antenna. The part of the asteroid closest to the antenna is at top. Credit: NASA/JPL-Caltech
The asteroid’s width in the images depends on the asteroid’s rotation rate and the antenna’s perspective. If the antenna stares directly down over the equator and the asteroid rotates rapidly, the images will be stretched from Doppler-shifting of the returned radar echo.
Radio waves are a form of light just like the familiar colors of the rainbow. If radio light is moving toward you, its waves bunch together more tightly and appear slightly bluer than if they were at rest. Astronomers call this a Doppler shift or blueshift. If they’re moving away, the light waves get stretched and become “redshifted”.
Three views of asteroid 4179 Toutatis made in early Dec. 2012 by Goldstone. In all three, distance from the antenna increases from top to bottom and Doppler frequency increases toward the right, indicating Toutatis rotates from right to left, since that’s the side of the asteroid approaching the observer. Credit: NASA/JPL-Caltech
A slow-rotating asteroid will appear narrower to radar eyes, and if it doesn’t rotate at all, will show up as a “spike” of light. When the antenna happens to be point directly at a pole, the asteroid will appear to be rotating neither toward nor away from the observer and also look like a spike.
Most asteroids fall somewhere in between, and their radar portraits are close to their true shapes. Radar images show us surface textures, shape, size, rotation rate and surface features like craters. 2013 ET joins the ranks of numerous asteroids probed by radio waves from Earth as we try to grasp the complexity of our planetary neighborhood while hoping for we don’t stare down cosmic disaster anytime soon.
Asteroid DA14 seen from the 2.1 Kitt Peak telescope as it departed the vicinity of Earth. Credit: NOAO/Nicholas Moskovitz (MIT)
Just as anticipated, on Friday, Feb. 15, asteroid 2012 DA14 passed us by, zipping 27,000 kilometers (17,000 miles) above Earth’s surface — well within the ring of geostationary weather and communications satellites that ring our world. Traveling a breakneck 28,100 km/hr (that’s nearly five miles a second!) the 50-meter space rock was a fast-moving target for professional and amateur observers alike. And even as it was heading away from Earth DA14 was captured on camera by a team led by MIT researcher Dr. Nicholas Moskovitz using the 2.1-meter telescope at the Kitt Peak National Observatory in Tucson, AZ. The team’s images are shown above as an animated gif (you may need to click the image to play it.)
This object’s close pass, coupled with the completely unexpected appearance of a remarkably large meteor in the skies over Chelyabinsk, Russia on the morning of the same day, highlight the need for continued research of near-Earth objects (NEOs) — since there are plenty more out there where these came from.
“Flybys like this, particularly for objects smaller than 2012 DA14, are not uncommon. This one was special because we knew about it well in advance so that observations could be planned to look at how asteroids are effected by the Earth’s gravity when they come so close.”
– Dr. Nicholas Moskovitz, MIT
The animation shows 2012 DA14 passing inside the Little Dipper, crossing an area about a third the size of the full Moon in 45 minutes. North is to the left.
(For a high-resolution version of the animation, click here.)
Exterior of the 2.1-meter telescope of the Kitt Peak National Observatory (NOAO/AURA/NSF)
According to the National Optical Astronomy Observatory, which operates the Kitt Peak Observatory, Dr. Moskovitz’ NSF-supported team “are analyzing their data to measure any changes in the rotation rate of the asteroid after its close encounter with the Earth. Although asteroids are generally too small to resolve with optical telescopes, their irregular shape causes their brightness to change as they rotate. Measuring the rotation rate of the asteroid in this way allows the team to test models that predict how the earth’s gravity can affect close-passing asteroids. This will lead to a better understanding of whether objects like 2012 DA14 are rubble piles or single solid rocks.
“This is critical to understanding the potential hazards that other asteroids could pose if they collide with the Earth.”
So just how close was DA14’s “close pass?” Well, if Earth were just a few minutes farther along in its orbit, we would likely be looking at images of its impact rather than its departure.*
Although this particular asteroid isn’t expected to approach Earth so closely at any time in the foreseeable future — at least within the next 130 years — there are lots of such Earth-crossing objects within the inner Solar System… some we’re aware of, but many that we’re not. Identifying them and knowing as many details as possible about their orbits, shapes, and compositions is key.
Even this soon after the Feb. 15 flyby observations of 2012 DA14 have provided more information on its orbit and characteristics., allowing for fine-tuning of the data on it.
According to the Goldstone Radar Observatory web page, the details on 2012 DA14 are as follows:
Semimajor axis 1.002 AU
Eccentricity 0.108
Inclination 10.4 deg
Perihelion distance 0.893 AU
Aphelion distance 1.110 AU
Absolute magnitude (H) 24.4
Diameter ~50 meters (+- a factor of two)
Rotation period ~6 h (N. Moskovitz, pers. comm.)
Pole direction unknown
Lightcurve amplitude ~1 mag (N. Moskovitz, pers. comm.)
Spectral class Ld (N. Moskovitz, pers. comm.)
Goldstone is currently conducting radar observations on the asteroid. A radar map of its surface and motion is anticipated in the near future.
A bright daytime meteor witnessed over Russia on Feb. 15, 2013 (RussiaToday)
Also, in an encouraging move by international leaders in the field, during the fiftieth session of the Scientific and Technical Subcommittee of the Committee on the Peaceful Uses of Outer Space, currently being held from at the United Nation Office in Vienna, near-Earth objects are on the agenda with a final report to be issued by an Action Team. Read the report PDF here.
*According to astronomer Phil Plait, while the orbits of Earth and DA14 might intersect at some point, on the 15th of February 2013 the asteroid slipped just outside of Earth’s orbit — a little over 17,000 miles shy. “It was traveling one way and the Earth another, so they could not have hit each other on this pass no matter where Earth was in its orbit,” he wrote in an email. Still, 17,000 miles is a very close call astronomically, and according to Neil deGrasse Tyson on Twitter, it “will one day hit us, like the one in Russian [sic] last night.” When? We don’t know yet. That’s why we must keep watching.
Radar images of asteroid 2007 PA8 acquired on October 28, 29 and 30. (NASA/JPL-Caltech/Gemini)
Take a good look at asteroid 2007 PA8 — over the past week it was making its closest pass of Earth for the next 200 years… and NASA’s 230-foot (70-meter) -wide Deep Space Network antenna at Goldstone, California snapped its picture as it went by.
All right, maybe no “pictures” were “snapped”… 2007 PA8 is a small, dark body that only came within four million miles (6.5 million kilometers) today, Nov. 5 (0.043 AU, or 17 times the distance from Earth to the Moon). But the radar capabilities of the Deep Space Network antenna in California’s Mojave Desert can bounce radar off even the darkest asteroids, obtaining data that can be used to create a detailed portrait.
In the image above, a composite of radar data acquired on October 28, 29 and 30, we can see the irregular shape of 2007 PA8 as it rotates slowly — only once every 3-4 days. The perspective is looking “down” at the 1-mile (1.6-km) -wide asteroid’s north pole, showing ridges and perhaps even some craters.
Although classified as a Potentially Hazardous Asteroid (PHA) by the IAU’s Minor Planet Center the trajectory of 2007 PA8 is well understood. It is not expected to pose any impact threat to Earth in the near or foreseeable future.
2007 PA8 was discovered by LINEAR on August 9, 2007.
