Tag Archives: radar

1998 QE2 asteroid flyby an opportunity for pros and amateurs alike

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Many separate telescopic images were combined to create this animation of asteroid 1998 QE2 moving through a star field this past week. Credit: Ernesto Guido and Nick Howes

An asteroid it would take an hour to walk across will speed past Earth on May 31 and provide radio astronomers a perfect opportunity to nab closeup views of its surface. 1998 QE2, discovered in 1998 by the Massachusetts Institute of Technology Lincoln Near Earth Asteroid Research (LINEAR) program,  will miss our planet by a healthy 3.6 million miles (5.8 million km) or 15 times the distance of the moon. Closest approach occurs at 3:59 p.m. Central time.

The asteroid’s large size combined with its relatively close approach makes it a great target for both the 230-foot (70-m) Goldstone radio dish and 1,000-foot (305-m) Arecibo dish in Puerto Rico. Lance Benner, the principal investigator for the Goldstone radar observations from NASA’s Jet Propulsion Laboratory in Pasadena, Calif., will have all hands on deck for the flyby. By sending bursts of radio waves at 1998 QE2 and measuring the retured radar echoes, Benner expects the dishes to resolve surface features as small as 12 feet (3.75m) across on the 1.7-mile-long asteroid (2.7 km).

The orbit of asteroid 1998 QE2. Its May 31 flyby will be the closest it comes to Earth for at least the next 200 years. Its closest point to the sun is similar to Earth’s; when farthest it’s 353 million miles from the sun in the asteroid belt between Mars and Jupiter. Credit: NASA/JPL-Caltech

Through an ordinary optical telescope, even a large one, 1998 QE2 will appear as a point of light. Radar observations reveal far more including shape, size, rotation and a wide variety of surface features. Goldstone observations are scheduled from May 30 – June 9; those at Arecibo for several days around June 5.

Already optical telescopes in the southern hemisphere have this monster rock in their crosshairs. By measuring repeating highs and lows in the asteroid’s brightness as it spins on its axis, astronomers can determine its rotation rate. 1998 QE2′s composition is gleaned by how it reflects sunlight. Reflected sunbeams streaming back to Earth carry the imprint of particular minerals that absorb and reflect portions of the sun’s light in unique ways that nail down their identities.

“It is tremendously exciting to see detailed images of this asteroid for the first time,” said Benner. “With radar we can transform an object from a point of light into a small world with its own unique set of characteristics. In a real sense, radar imaging of near-Earth asteroids is a fundamental form of exploring a whole class of solar system objects.”

1998 QE2 looks like a point of light in this time exposure taken remotely with a telescope in Australia by the team of Ernesto Guido and Nick Howes. The asteroid is currently very faint and only visible in the southern hemisphere. Click for more on the asteroid in their blog.

I’m excited about the asteroid because it will be bright enough to be visible in small telescopes across both northern and southern hemispheres for several nights around the time of closest approach. Between May 30 and June 5 it will shine at 10.5-11.0 magnitude while chugging through the constellations Libra and Ophiuchus, both conveniently placed at nightfall. Its steady movement across the sky – 2/3 of a full moon diameter an hour – will be obvious through the telescope. Come the end of the month, I’ll create a map to help you find it.

Read more about 1998 QE2 HERE. Amateur astronomers needing orbital elements and ephemerides can check out the Goldstone planner.

Curious about asteroids? Tune in to tonight’s live stream by expert Lance Benner

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Nine radar images of near-Earth asteroid 2007 PA8 were obtained between Oct. 31 and Nov. 13, 2012, by NASA’s 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, Calif. Credit: NASA/JPL-Caltech

Ever wonder how scientists get such detailed radar images of asteroids that only look like points of light in optical telescopes? Tune in tonight or tomorrow night to a talk by Dr. Lance Benner, research scientist at the Jet Propulsion Lab, to find out. Benner will speak on Radar Imaging of Near Earth Asteroids at Pasadena City College; you can watch the real-time webcast and even join the audience for questions after the talk. Both lectures start at 9 p.m. Central (7 p.m. Pacific) time May 9 and 10.

Dr. Lance Benner. NASA photo

Only two radio telescopes on the planet are used for radar imaging of asteroids: the giant 1,000-foot (305 m) Arecibo Observatory in Arecibo, Puerto Rico and the 230-foot (70 m) Goldstone dish in JPL’s Deep Space Network in California’s Mojave Desert. By pinging nearby asteroids with radio waves and studying the reflected radio echoes, these telescopes can resolve details as small as 10 feet (3 m) across.

Radar images can also nail down an asteroid’s rotation rate, measure its position with great precision (allowing for a more precise orbit to be calculated) and “see” features like craters and boulders.

In a related story, Detlef Koschny, Head of Near-Earth Object activities in the European Space Agency’s Space Situational Awareness Programe Office, hopes to improve efforts to find and track near-Earth objects (NEOs) using telescopes operated by European Union members to scan the sky nightly for new Earth-approaching asteroids. The agency is also considering ways of deflecting smaller but still potentially dangerous asteroids should they be found on a collision course with Earth.

“It’s important that we become aware of the current and future position of NEOs, develop estimates on the likelihood of impacts and assess the possible consequences,” says Koschny.

Artist’s view of Earth-approaching asteroids. Many asteroids in this class were originally located a safe distance away in the asteroid belt between Mars and Jupiter, but collisions between them created fragments that were later perturbed by the planet Jupiter into Earth-crossing orbits. Credit: ESA / P. Carril

Of the more than 600,000 known asteroids in the solar system, nearly 10,000 are classified as Near Earth Asteroids because they pass relatively close to our planet. “Near” is defined as any object approaching within 28 million miles of Earth’s orbit.

This week in a meeting in Spain, Deimos Space, an industrial partner working for ESA, invited top researchers from universities, research institutes, national space agencies and industry in Europe and the USA to discuss the state of the art in NEO impact effects and threat mitigation.

There are a variety of methods being considered for changing a potentially hazardous asteroid’s course, and they all critically depend on finding the object well in advance of a collision.

You can hit it with a massive object the way we smacked Comet Tempel 1 with an 815-lb hunk of copper during NASA’s Deep Impact Mission in 2005. If the asteroid’s small enough and impactor massive enough, you could nudge the object off its hazardous course.

Artist view of a spacecraft acting as a gravity tractor nudging an asteroid off-course through mutual gravitational interaction. Earth and moon are off to the right. Credit: Dan Durda/FIAAA/B612 Foundation

Or you could vaporize part of the asteroid with a nuclear weapon, altering its orbit while hopefully not creating additional fragments that could imperil the planet. For obvious reasons, this method would work best with asteroid made of solid rock, not those made of loose “rubble piles”.

Then there’s the gravitational tug method. Here you orbit a large, heavy spacecraft near the asteroid. The mutual gravitational attraction between the two over several years time would change the space rock’s trajectory. A variation on this approach is to fire the spacecraft’s thrusters at the object or even to anchor a rocket engine directly to the asteroid’s surface and blast away, giving it a slow, steady push in the right direction.

Other methods proposed include playing “asteroid paintball” by dusting an NEA with black soot or white powder or even wrapping it in shiny aluminized plastic. Think of how hot you’d feel wearing a black shirt on a sunny day compared to a white one. Absorption or reflection of sunlight can change an asteroid’s rotation rate and nudge it into a slightly different orbit over time.

Expand your knowledge on the topic of asteroids by listening in tonight or tomorrow night to Dr. Benner’s talk. There are actually two ways to connect – the live stream and also via Flash Player with open captioning.

Go for a virtual asteroid ride; seismic activity on 2012 DA14?

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Asteroid 2012 DA14, which will pass about 17,200 miles from Earth tomorrow (Fri. Feb. 15) around 1:24 p.m. CST is about 150 feet long or somewhat less than half the length of a football field. Illustration: Bob King using wiki and NASA images

As asteroid 2012 DA14 silently flies toward Earth, how would you like to go along for the ride? Now you can, virtually speaking. NASA has created a simulated display that allows you to accompany the asteroid as it speeds toward the planet. Since the view refreshes every two minutes, you can watch the planet grow larger as the asteroid sweeps in to make its closest approach tomorrow around 1:24 p.m. Central Time. That’s when the real drama will unfold as 2012 DA14 passes just 17,200 miles over Indonesia before speeding back into the depths of space. Click HERE to make the trip.

Although 2012 DA14 won’t impact Earth, the planet’s gravity will leave a potentially strong impression on the asteroid. Besides bending its orbit into a smaller circle with a shorter orbital period during the flyby, it’s possible that the space rock might tremble with tremors or asteroid-quakes.

View from the virtual asteroid tracker looking toward Earth today Feb. 14, 2013 at 1:37 p.m., one day before closest approach. Credit: NASA

“We are going to be looking closely for evidence of seismic activity on 2014 DA14 as it passes by,” says Richard Binzel, a professor of planetary science at MIT. “This is the first case of an object coming close enough to experience quakes AND where we have enough notice to plan observations.”

The Galileo spacecraft captured this “stretched color” view of asteroid 951 Gaspra in 1991. The red color is caused by solar radiation and cosmic rays weathering of the asteroid’s soil. Credit: NASA

A few years ago Binzel noticed a small group of asteroids that didn’t show signs of “space weathering” from bombardment by cosmic rays and solar radiation over the eons. High-energy particles interact with asteroids’ rocky surfaces and cause their soils to turn dark-red.

After studying their orbits, he discovered that all these “fresh-faced” space rocks had had close encounters with the Earth in the past million years.

“We believe they were ‘shaken up’ by their encounters with Earth,” he says. “Gravitational forces during the flybys can stretch, rattle, and torque these asteroids, causing dark, space-weathered material on the surface to be overturned, revealing the fresh stuff underneath.”

NASA’s Goldstone radar dish in California will have its eye trained on the asteroid during tomorrow’s flyby. The dish sends radio waves at the asteroid and measures their echo or reflection upon return to build up a map of its shape. Credit: NASA

2012 DA14′s crust could shift by an inch or two and possibly release a puff of asteroid dust. MIT postdoc Nick Moskovitz, who works with Binzel, is coordinating observations with worldwide observatories to pin down the color, spin, shape, and reflectivity of the asteroid as it passes by. NASA’s 70-meter Goldstone radar dish will also repeatedly ping 2012 DA14 with radio waves and measure the energy reflected back to create a 3D picture of it. If we’re very fortunate, the dish might even see the effects of seismic activity. Read more on the topic HERE.


Nice video about the flyby from NASA’s ScienceCast

Chinese probe to make daring flyby of asteroid Toutatis

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Illustration of the Chang’e 2 probe flyby of Toutatis next week. Chang’e 2 originally was used to map the moon and then repurposed for the asteroid flyby. Chang’e is named after an ancient Chinese moon goddess. Credit: Andrzej Mirecki

If all goes according to plan, one week from today on Dec. 13, the Chinese Chang’e 2 probe will snap closeup photos of near-Earth asteroid 4179 Toutatis (too-TAT-us) from only 200 miles away. Toutatis will be making its own close approach the day before, zooming by Earth at a distance of 4.3 million miles.

Traveling at about 7 miles a second, the ship will have only the briefest of opportunities to shoot photos as it rapidly approaches and then departs the asteroid. High-resolution cameras should resolve features tens of meters (~65 to 150 feet) across, giving us our most detailed optical views ever of this 3-mile-long space rock shaped like a bowling pin.


Click to watch Toutatis’ topsy-turvy rotation. Images from NASA radar

Our best “photos” to date are a series of remarkable images made by beaming radio waves at the asteroid during previous close approaches and analyzing the reflected echoes. Those images reveal an irregular body with two pronounced lobes that may once have been two separate asteroids. Possibly an older asteroid was broken apart during an earlier collision, pieces later reassembling to form present-day Toutatis.

Unlike the planets, which spin on one axis in one direction, Toutatis spins about two axes, wobbling about like a poorly-thrown football pass. If you stood on the asteroid’s surface, the sun would rise at random times along random points on the horizon. Makes me dizzy just thinking about it.

Toutatis is a rocky asteroid about 3 miles long. These 1992 radar images from NASA’s Goldstone radar dish reveal an undulating surface, craters and two large lobes that may have once been separate asteroids. Courtesy Steve Ostro, JPL

Toutatis orbits the sun every 4 years in nearly the same plane as Earth’s orbit and is a frequent visitor to the inner planets. When closest to the sun, it’s located just inside Earth’s orbit; when farthest it travels among its fellow asteroids in the outer fringes of main asteroid belt between Mars and Jupiter.

Every four years Toutatis passes through our neighborhood, which is why it’s designated as a PHA or potentially hazardous asteroid. PHAs are asteroids that come within 5 million miles of Earth and are large enough to survive atmospheric entry and cause major destruction.

Radar picture of Toutatis taken by the Goldstone antenna on Dec. 3, 2012 as part of the 2012 campaign (see below). Credit: NASA/JPL

Toutatis is the largest asteroid we know of that approaches Earth most closely. That doesn’t mean it’s going to hit us, only that a collision is remotely possible. Calculations based on many observations since its discovery in 1989 have ruled out any chance of a hit for at least the next six centuries. Rest easy.

Toutatis came as close as 967,000 miles or just shy of 4 lunar distances on September 29, 2004. This time around, it will draw to within 4.3 million miles, more than four times farther away but still be bright enough at 10.5 magnitude to be seen in a small telescope. I’ll provide directions on how to find it early next week.The next time the asteroid makes a close close approach to Earth will be in November 2069 (7.7 lunar distances).

Toutatis is shown on Dec. 12 when nearest Earth. Its orbit (in blue) takes the asteroid to just within Earth’s orbit to well beyond Mars. Credit: JPL

The 230-foot radar dish at Goldstone has already swung in Toutatis’ direction and made early images of the flyby in a special 2012 campaign to better model its rotation, shape and surface features. Combined with the pictures from Chang’e 2, we’ll soon have a clearer portrait of this unique object.

Users guide to Tuesday night’s flyby of asteroid 2005 YU55

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This radar image of asteroid 2005 YU55 was generated from data taken in April of 2010 by the Arecibo Radar Telescope in Puerto Rico. Image credit: NASA/Cornell/Arecibo

It’s not unusual to have small asteroids pass closer to the Earth than the moon’s distance of 240,000 miles. Matter of fact, the house-sized 2011 UX255 buzzed only 96,000 miles from our planet last Friday and little 2011 MD gave us a close shave at just 7,500 miles on June 27. Next up is 2005 YU55. This one’s bigger than most at 1,300 feet or 400 meters in diameter, and will jitterbug across the evening sky next Tuesday night November 8 at a distance of 205,000 miles or about 4/5 the way to the moon. The orbit of the asteroid makes it a regular in the neighborhood, but this is the closest it’s come in the past 200 years.

As with the earlier asteroids, 2005 YU55 poses no threat to Earth now and for at least the next 100 years. Astronomers have used radar to refine its orbit with great precision so there’s no cause for concern. Nor will the space rock’s gravitational pull have any detectable effects on Earth. But if our featured asteroid did strike the planet, it would make a good mess of things, since even a relatively small object has tremendous energy due to its cosmic velocity of many thousands of miles per hour. It’s estimated that 2005 YU55 would tear into the planet with the equivalent explosive power of 60 hydrogen bombs.

The asteroid 2005 YU55 moves closer to our planet each day. Today it's 5.1 million miles away. Beware! Objects appear closer than they really are. Credit: NASA

2005 YU55 is darker than a charcoal briquette,  nearly spherical and makes one spin on its axis about every 18 hours. NASA scientists will be tracking it with its 230-foot Deep Space Network radio telescope at Goldstone, California beginning this Friday the 4th. Tracking will continue at Goldstone for at least four hours each day from Nov. 6 through Nov. 10. Radar observations from the Arecibo Planetary Radar Facility in Puerto Rico will begin on Nov. 8, the same day the asteroid will make its closest approach to Earth.

Scientists are hoping to use the flyby as an ideal opportunity to map the asteroid’s surface by pinging it with radio waves and then collecting the returned signals. Analysis of the data will help them build a map showing details as small as 7 feet across as well as provide information about the object’s shape, size and composition. The pictures are reminiscent of  sonograms and employ a similar echo-sensing technology. The more we learn about near-Earth approaching asteroids like 2005 YU55, the better equipped we’ll be to understand and plan for any future asteroids that might pass too close for comfort.

The green box in this wide view of the sky the night of Nov. 8 shows the portion of sky the asteroid will zip through between the hours of 8 and 9 p.m. Central Standard Time. Center your telescope on 13 and 9 Pegasi, then use the detailed charts below to star-step to the asteroid. Maps created with Stellarium

To spot this speedy space rock next Tuesday evening, you’re going to need a telescope. At brightest, it will shine at magnitude 11.2 or five levels below what the naked eye can see. Seasoned observers can track it in a scope as small as 3-inches, but most will need a 6-inch or larger instrument simply because a bright gibbous moon will be in the same region of sky. Moonlight has this bad habit of hiding fainter stars. You’ll also need a good star map and stick-to-itiveness, because 2005 YU55 will be traveling up to 7 arc seconds per second. That translates to one full moon diameter (one-half degree) in just under five minutes. Zippy!

Detailed view showing the asteroid's path every 10 minutes from 8-8:30 p.m. CST through the stars of Pegasus beginning just south of 9 and 13 Pegasi (top). Stars are shown to 12th magnitude. North is up and east to the left. Many telescopes invert the view, so remember to flip the map upside down if you're using a reflector.

Once found, the asteroid will appear at medium and high magnifications to move continuously like a faint satellite. I’ve watched a few close asteroid approaches and it’s very exciting to see a cosmic object move so rapidly. As you gaze through into the eyepiece, it dawns on you that you’re looking at a flying rock the size of a battleship a “hair’s breadth” from the home planet. Suddenly those twinkly little lights in the solar system feel much more real.

The asteroid is best seen from the U.S., where it will fly through the constellations Delphinus and Pegasus high in the southern sky from the time of closest approach through the remainder of the night. European observers can catch it early on in the constellations Serpens and Aquila, but it will be farther away and fainter with a magnitude between 13 and 14. Closest approach to Earth occurs around 5:30 p.m. CST Tuesday Nov. 8. That’s 12:30 a.m. Nov. 9 across most of central Europe, where the asteroid will still be visible but located low in the western sky.

This second map shows the asteroid's flight between 8:30 and 9 p.m. CST. Remember to add one hour for EST, subtract one hour for MST and two hours for PST. The path in both maps is drawn for Kansas City and the central U.S.

The very best map I’ve seen for tracking the space rock is on page 53 of the November 2011 issue of Sky and Telescope magazine. Because 2005 YU55 will be so close, it takes a slightly different track across the sky depending on where you live, similar to holding your index finger at arm’s length and watching it shift back and forth as you open and close either eye. The Sky and Telescope map includes a little map of the U.S. placed on the asteroid’s path that helps compensate for this shifting effect called parallax. If you don’t have access to the magazine, you can use the maps I created, which are based on the same information. UPDATE: Online version of the Sky and Telescope chart is now up.

The position of the moon in relation to the Pleiades cluster is shown from four widely separated places on Earth. Objects close to the Earth shift position against the distant background stars depending on your location. Credit: Tom Ruen

Positions are shown at 10-minute intervals – I did say it was moving fast – for Kansas City and central regions of the country. If you live in the far southern U.S., the asteroid’s path will lie almost 1/4 degree above (north of) the line and 1/4 degree below (south of) the line if you live along the northern border. And if you’re on the West Coast, the asteroid will be about 3 minutes ahead of the times shown. East Coasters will see it 2 minutes behind those times. Let’s do an example.

Someone living near New York City planning to see 2005 YU55 at 9 p.m. local time should look for it 2 minutes shy of the 8:00 p.m. map position. An observer in San Francisco looking at 6 p.m. local time would point their scope 3 minutes past the 8:00 p.m. mark.

If you have sky charting software like MegaStar, SkyOrb, SkyMap, Redshift, Guide and others, you can plot your own site-specific maps of the asteroid’s path by opening up your asteroid menu and adding 2005 YU55 and its orbital elements. Here are the latest elements from the JPL Horizons website:

* Epoch: 2011 November 13
* Mean anomaly (M) = 50.3717704
* Semi-major axis (a) = 1.1574416520
* Eccentricity (e) = .430606239
* Argument of perihelion = 273.574761
* Longitude ascending node = 35.9342364
* Inclination (i) = .34122817
* Equinox 2000
* H = 21.92, G=0.15

The good thing is that 2005 YU55 is fairly bright and will remain near it maximum brightness for much of the night. Even if you don’t compensate for parallax, just center your scope on one of the times shown and wait and watch. If you examine the field of view carefully, you should notice that one of the “stars” is slowly moving to the east after a minute or two.  Congratulations – you’ve just found the asteroid! Now stay on its tail and enjoy the ride.