Vesta Full Frame

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.

The “Snowman” on Vesta
Image Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA
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.

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.

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:

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.