Amateur Astronomers Will Help ‘Target Asteroids!’

A new NASA outreach project will enlist the help of amateur astronomers to discover near-Earth objects (NEOs) and study their characteristics. NEOs are asteroids with orbits that occasionally bring them close to the Earth.

The amateur astronomers are about to make observations that will affect current and future space missions to asteroids. Some will use custom-made, often automated, telescopes equipped with CCD cameras in their backyards. Others will use home computers to make remote observations with more powerful telescopes states or continents away. Many belong to leading national and international amateur astronomy organizations with members ranging from retirees to school kids.

Researchers on NASA’s robotic asteroid sample return mission, OSIRIS-REx, are turning to amateur astronomers for new data on near-Earth asteroids in a citizen science observing campaign called “Target Asteroids!” The campaign starts in April 2012 and will last at least to the end of this decade.

The full name of the OSIRIS-REx mission is Origins Spectral Interpretation Resource Identification Security – Regolith Explorer. The OSIRIS-REx spacecraft is to launch in 2016, reach a well-characterized primitive asteroid called (101955) 1999 RQ36 in 2019, examine that body up close during a 505-day rendezvous, then return at least 60 grams of it to Earth in 2023.

“Asteroids are a rich and accessible historic archive of the origin of our Solar System and life, a valuable source of mineral resources, and potentially hazardous Earth impactors that civilization must learn to deal with,” said OSIRIS-REx Principal Investigator Dante Lauretta of the University of Arizona. “Our mission will address all these issues.”

1999 RQ36 — a 500-meter-diameter, dark carbonaceous asteroid — is difficult for even powerful Earth-based telescopes to observe at this time because it is relatively distant from Earth.

“Amateur astronomers are asked to observe asteroids selected because they are in near-Earth orbits that can be reached by current-generation spacecraft and are at least 200 meters in diameter,” said Target Asteroids! scientist Carl Hergenrother, head of the OSIRIS-REx astronomy working group.

“Precise orbits, sizes, rotation rates, physical composition and other important characteristics for these asteroids are largely unknown, ” Hergenrother said.

“We want amateur astronomers to do astrometry (which precisely measures positions of objects), photometry (which measures brightness) and spectroscopy (which measures the colors, or wavelengths, of light) to discover as much as we can about these objects,” he said.

“These will be challenging objects to observe because they are very faint,” said Target Asteroids! coordinator Dolores Hill of the OSIRIS-REx education and public outreach program. “Amateur astronomers may have to make what are called ‘track and stack’ observations,” a technique that acquires and adds multiple short images.

“One of the major goals of having amateur astronomers on board is they can observe these objects every night, unlike professional astronomers who may get to telescopes once every few nights, or more typically once a month or every three months,” Hergenrother said.

People don’t need to own their own telescopes or live under clear skies to work on Target Asteroids!, Hergenrother and Hill emphasized.

For not much money, observers can now go online and sign up to use a growing network of quality robotic telescopes sited at some of the choicest astronomical spots in the country, they added.

Scientists will compare data from amateur and professional astronomers’ ground-based observations with data from OSIRIS-REx spacecraft instruments to learn more about Earth-crossing asteroids and identify likely candidates for future asteroid missions, they said.

For more information see the Target Asteroids! web page.

KISS My Asteroid

Here is the Introduction to “Asteroid Retrieval Feasibility Study” by the Keck Institute for Space Studies (KISS) at the Jet Propulsion Laboratory, released April 2, 2012, and available on the National Space Society asteroid page under the “See also” section.

Illustration of an asteroid retrieval spacecraft in the
process of capturing a 7-m, 500-ton asteroid.
(Image Credit: Rick Sternbach / KISS)

The idea to exploit the natural resources of asteroids is older than the space program. Konstantin Tsiolkovskii included in The Exploration of Cosmic Space by Means of Reaction Motors, published in 1903, the “exploitation of asteroids” as one of his fourteen points for the conquest of space. More recently this idea was detailed in John Lewis’ book Mining the Sky, and it has long been a major theme of science fiction stories. The difference today is that the technology necessary to make this a reality is just now becoming available. To test the validity of this assertion, NASA sponsored a small study in 2010 to investigate the feasibility of identifying, robotically capturing, and returning to the International Space Station (ISS), an entire small near-Earth asteroid (NEA) – approximately 2-m diameter with a mass of order 10,000 kg – by 2025. This NASA study concluded that while challenging there were no fundamental show-stoppers that would make such a mission impossible. It was clear from this study that one of the most challenging aspects of the mission was the identification and characterization of target NEAs suitable for capture and return.

In 2011 the Keck Institute for Space Studies (KISS) sponsored a more in-depth investigation of the feasibility of returning an entire NEA to the vicinity of the Earth. The KISS study focused on returning an asteroid to a high lunar orbit instead of a low-Earth orbit. This would have several advantages. Chief among these is that it would be easier from a propulsion standpoint to return an asteroid to a high lunar orbit rather than take it down much deeper into the Earth’s gravity well. Therefore, larger, heavier asteroids could be retrieved. Since larger asteroids are easier to discover and characterize this helps to mitigate one of the key feasibility issues, i.e., identifying target asteroids for return. The KISS study eventually settled on the evaluation of the feasibility of retrieving a 7-m diameter asteroid with a mass of order 500,000 kg. To put this in perspective, the Apollo program returned 382 kg of moon rocks in six missions. The OSIRIS-REx mission [6] proposes to return at least 60 grams of surface material from a NEA by 2023. The Asteroid Capture and Return (ACR) mission, that is the focus of this KISS study, seeks return a 500,000-kg asteroid to a high lunar orbit by the year 2025.

The KISS study enlisted the expertise of people from around the nation including representatives from most of the NASA centers (ARC, GRC, GSFC, JPL, JSC, and LaRC), several universities (Caltech, Carnegie Mellon, Harvard, Naval Postgraduate School, UCLA, UCSC, and USC), as well as several private organizations (Arkyd Astronautics, Inc., The Planetary Society, B612 Foundation, and Florida Institute for Human and Machine Cognition). The people listed below participated in the KISS study and developed the contents of this report. The study was conducted over a six-month period beginning with a four-day workshop in September 2011 followed by a two-day workshop in February 2012, and concluding with the submission of this report in April 2012.

Vesta Full Frame

Vesta
Vesta Image from 5,200 kilometers
Image Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA
See also full rotation movie of Vesta.

The Dawn spacecraft has completed imaging of Vesta from an altitude of 5,200 kilometers and has begun spiraling down to an altitude of 2,700 kilometers for the first series of scientific observations.

Chris Russell, Dawn’s principal investigator at UCLA, notes:

We have been calling Vesta the smallest terrestrial planet. The latest imagery provides much justification for our expectations. They show that a variety of processes were once at work on the surface of Vesta and provide extensive evidence for Vesta’s planetary aspirations.

Below are additional images of Vesta from the 24 July collection.

Vesta
The “Snowman” on Vesta
Image Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA
Vesta
The Southern Hemisphere of Vesta with a multitude of craters
Image Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA

Is an Earth Trojan Asteroid the Logical Target for the "Flexible Path"?

Trojan Asteroid 2010 TK7
Asteroid 2010 TK7 is circled in green.
Image Credit: NASA / JPL-Caltech / UCLA
Scientists using the Wide-field Infrared Survey Explorer (WISE) have discovered the first Trojan Asteroid in Earth orbit. Trojans orbit at a location in front of or behind a planet known as a Lagrange Point.

A video of the asteroid and its orbit at the Lagrange point can be found here.

Martin Connors of Athabasca University in Canada is the lead author of a new paper on the discovery in the July 28 issue of the journal Nature.

Connors notes that:

These asteroids dwell mostly in the daylight, making them very hard to see. But we finally found one, because the object has an unusual orbit that takes it farther away from the sun than what is typical for Trojans. WISE was a game-changer, giving us a point of view difficult to have at Earth’s surface.

TK7 is roughly 300 meters in diameter and traces a complex motion around SEL-4 (Sun Earth Lagrange point 4). The asteroid’s orbit is stable for at least the next 100 years and is currently about 80 million kilometers from the Earth. In that time, it is expected to come no closer that 24 million kilometers.

The obvious question is whether this is the logical destination for NASA’s Flexible Path manned asteroid mission? The Lagrange 4 point (SEL-4) is a logical way station on the Solar System exploration highway. Other NEO asteroids that have been identified as possible targets are few and much more difficult to reach and return than an asteroid located directly at SEL-4 would be. An asteroid located there could well be the target of opportunity that opens manned exploration of the Solar System in an “easy” mode. Unfortunately, Asteroid 2010 TK7 would not serve as such a target because it travels in an eccentric orbit around SEL-4 so far above and below the plane of Earth’s orbit that it would require very large amounts of fuel to reach.

NEOWISE is the program for searching the WISE database for Near Earth Objects (NEO), as well as other asteroids in the Solar System.The NEOWISE project observed more than 155,000 asteroids in the main belt between Mars and Jupiter, and more than 500 NEOs, discovering 132 that were previously unknown.

NASA's WISE Mission Finds First Trojan Asteroid Sharing Earth's Orbit

PASADENA, Calif. – Astronomers studying observations taken by NASA’s Wide-field Infrared Survey Explorer (WISE) mission have discovered the first known “Trojan” asteroid orbiting the sun along with Earth.

Trojans are asteroids that share an orbit with a planet near stable points in front of or behind the planet. Because they constantly lead or follow in the same orbit as the planet, they never can collide with it. In our solar system, Trojans also share orbits with Neptune, Mars and Jupiter. Two of Saturn’s moons share orbits with Trojans.

Scientists had predicted Earth should have Trojans, but they have been difficult to find because they are relatively small and appear near the sun from Earth’s point of view.

“These asteroids dwell mostly in the daylight, making them very hard to see,” said Martin Connors of Athabasca University in Canada, lead author of a new paper on the discovery in the July 28 issue of the journal Nature. “But we finally found one, because the object has an unusual orbit that takes it farther away from the sun than what is typical for Trojans. WISE was a game-changer, giving us a point of view difficult to have at Earth’s surface.”

The WISE telescope scanned the entire sky in infrared light from January 2010 to February 2011. Connors and his team began their search for an Earth Trojan using data from NEOWISE, an addition to the WISE mission that focused in part on near-Earth objects, or NEOs, such as asteroids and comets. NEOs are bodies that pass within 28 million miles (45 million kilometers) of Earth’s path around the sun. The NEOWISE project observed more than 155,000 asteroids in the main belt between Mars and Jupiter, and more than 500 NEOs, discovering 132 that were previously unknown.

The team’s hunt resulted in two Trojan candidates. One called 2010 TK7 was confirmed as an Earth Trojan after follow-up observations with the Canada-France-Hawaii Telescope on Mauna Kea in Hawaii.

The asteroid is roughly 1,000 feet (300 meters) in diameter. It has an unusual orbit that traces a complex motion near a stable point in the plane of Earth’s orbit, although the asteroid also moves above and below the plane. The object is about 50 million miles (80 million kilometers) from Earth. The asteroid’s orbit is well-defined and for at least the next 100 years, it will not come closer to Earth than 15 million miles (24 million kilometers).

Larger image here. Animation of orbit here.
Earth Trojan Asteroid’s Eccentric Orbit.
Larger image here.
Animation of orbit here.

“It’s as though Earth is playing follow the leader,” said Amy Mainzer, the principal investigator of NEOWISE at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Earth always is chasing this asteroid around.”

A handful of other asteroids also have orbits similar to Earth. Such objects could make excellent candidates for future robotic or human exploration. Asteroid 2010 TK7 is not a good target because it travels too far above and below the plane of Earth’s orbit, which would require large amounts of fuel to reach it.

“This observation illustrates why NASA’s NEO Observation program funded the mission enhancement to process data collected by WISE,” said Lindley Johnson, NEOWISE program executive at NASA Headquarters in Washington. “We believed there was great potential to find objects in near-Earth space that had not been seen before.”

NEOWISE data on orbits from the hundreds of thousands of asteroids and comets it observed are available through the NASA-funded International Astronomical Union’s Minor Planet Center at the Smithsonian Astrophysical Observatory in Cambridge, Mass.

JPL manages and operates WISE for NASA’s Science Mission Directorate in Washington. The principal investigator, Edward Wright, is a professor at the University of California, Los Angeles. The mission was selected under NASA’s Explorers Program, which is managed by the agency’s Goddard Space Flight Center in Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory in Logan, Utah.

The spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

For more WISE information visit: http://www.nasa.gov/wise.

Craters on Vesta

Vesta Craters
Craters on Vesta
Image Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA

NASA’s Dawn spacecraft obtained this image of the protoplanet Vesta with its framing camera on July 18, 2011. It was taken from a distance of about 10,500 kilometers. The smallest detail visible is about 2.0 km.

In August, Dawn will begin sending images from its high resolution camera.

Dawn Spacecraft Enters Orbit around Asteroid Vesta July 15

NASA’s Dawn spacecraft will enter orbit around the second most massive (but third largest) asteroid in the asteroid belt at around 10 pm Pacific Daylight Time Friday July 15. It will stay in orbit around Vesta for about a year and then move on to orbit the largest asteroid, Ceres. This demanding mission profile is made possible by using ion propulsion.

Vesta as imaged on July 9 by the Dawn spacecraft, courtesy NASA
Vesta as imaged on July 9 by the Dawn spacecraft, courtesy NASA

Vesta

Dimensions: About 578 by 560 by 458 kilometers (359 by 348 by 285 miles) – about the length of Arizona
Rotation: Once every 5 hours, 20 minutes
Composition: Rocky

Ceres

Size: 975 by 909 kilometers (606 by 565 miles)
Rotation: Once every 9 hours, 4.5 minutes
Composition: Believed to have large quantities of ice

More information.

Mission to Asteroid Itokawa – The Seven Year Voyage

ISDC conference report by Dave Fischer

Professor Jun’ichiro Kawaguchi presented the history and results of the Hayabusa program, formally known as MUSES-C. Kawaguchi Professor Kawaguchi is the Program Manager for the MUSES-C program at the Lunar and Planetary Exploration Program Group at JAXA.

The spacecraft was launched on 9 May 2003. It was primarily an engineering demonstration project, with the following objectives:

  • 1. Interplanetary cruise via ion engines as the primary propulsion system
  • 2. Autonomous navigation and guidance using optical measurements
  • 3. Sample collection from an asteroid surface under micro gravity
  • 4. Direct reentry for the sample recovery capsule from interplanetary orbit
  • 5. Combination of low thrust and gravity assist for interplanetary missions

The spacecraft was relatively small with dimensions of 1.0m x 1.6m x 1.1m. It weighed a total of 510 kg, of which 380 kg was the spacecraft, instruments and engines, 70 kg of chemical fuel for thrusters and 60 kg of Xenon for the ion propulsion system. The engine was composed of four chambers, each of which developed seven (7) millinewtons of thrust with an isp of 3,000 seconds.

Professor Kawaguchi noted that the mission mostly entailed overcoming obstacles. He presented the following time line illustrating the issues encountered and solved:

  • 2004 Fall – Largest solar flare ever of class X25.
  • 2005 August – One Reaction wheel lost.
  • Arrival at Itokawa.
  • 2005 October – Second Reaction Wheel lost.
  • 2005 November – Fuel leak after the second touchdown.
  • 2005 December – Gas eruption tumbled the space craft. Contact was lost for seven weeks.
  • 2005 December – Functioning of the chemical engines was lost. Battery went dead.
  • 2006 January – Restoration of attitude control with Xenon cold gas.
  • 2006 – Refurbish operation. New attitude control established via Solar Radiation Torque. Charged the battery.
  • 2007 January – Closing of the capsule lid succeeded.
  • 2007 – First half of the ion engine delta-v burn completed.
  • 2009 March – April – Second half of the ion engine delta-v burn completed.
  • 2009 November – Ion engine emergency stop due to “End of Life”.
  • 2009 November – New ion engine configuration worked
  • 2010 June 13 – Final four burns and Re-entry and Recovery of the Capsule.

One of the major accomplishments of the Hayabusa mission was the demonstration of the navigation capabilities of the instruments related to surface detection and ranging. To this end, three markers were deployed as references in order to help zero out horizontal velocity. Using observations by the spacecraft for navigation, positioning improved by 1000%. Horizontal velocity was controlled to within one (1) centimeter per second (cm/s) and position was determined within 10 meters.

The goal was to land on the central (relatively) smooth portion of the asteroid. Eventually, Hayabusa touched down within 500 meters of the original target selected at the beginning of the mission.

One of the major achievements using the navigation system was the placement of the markers, followed by the return to one of them a week later. This was shown by the photographs taken of Itokawa and the navigation markers by the camera aboard Hayabusa:

Itokawa
White Navigation Marker placed 20 November 2005
Shadow of Hayabusa upon Autonomous Return on 26 November 2005.
Image Credit: JAXA

Professor Kawaguchi then discussed the scientific results from the mission. Initial observations from the return capsule did not show much. Eventually, about 1500 particles from Itokawa were recovered. All were smaller than 100 micrometers. Researchers across Japan took 52 of these particles and applied a range of microanalytical techniques – XRD, XRF, UMT, FIB, TEM, SEM, EPMA and SIMS. This alphabet soup clearly showed that Itokawa was a space-weathered ordinary LL chondrite asteroid. [Note: the results were presented at the Lunar and Planetary Science Conference in The Woodlands, Texas, from 7 – 11 March 2011]

Professor Kawaguchi also commented that a follow on mission – Hayabusa 2 – is in the works for the 2014 timeframe.