In its collecting configuration, the Genesis spacecraft exposed several types of solar wind collectors as well as solar wind ion and electron monitors. (Courtesy NASA/JPL-Caltech)

The Genesis spacecraft collected a sample of solar wind and returned it to Earth for analysis. It was the first NASA "sample return mission" to return material since the Apollo Program, and the first to return material from beyond the orbit of the Moon. It was launched on August 8, 2001, and crash-landed on September 8, 2004 after a design flaw prevented the deployment of its drogue parachute. The crash contaminated many of the sample collectors but, although most were damaged, a large fraction of the collectors were recovered.^[1] The science team demonstrated that some of the contamination could be removed, that some could be avoided, and that solar-wind could be analyzed using a variety of approaches.^[2] It is relatively easy to see the solar wind, but the precision measurements are difficult and techniques are still being refined in laboratories worldwide. Still, as of March 2008 there was reason to believe that all of the mission's major science objectives will be achieved successfully.^[3]

[edit] Objective

A Genesis collector array in the Genesis clean lab at the Johnson Space Center (photo courtesy NASA). Hexagons consist of a variety of ultra-pure, semiconductor-grade wafers, including silicon, commercial “sapphire” (i.e. corundum), gold on sapphire, diamond-like carbon films,^[4] and other materials. ^[5]

The Mission’s primary science objectives as paraphrased from the original proposal fact sheet^[6] were to:

• Obtain precise solar isotopic abundances of ions in the solar wind, as essentially no data having a precision sufficient for solving planetary science problems are available.
• Obtain greatly improved solar elemental abundances by factor of 3-10 in accuracy over what is in the literature.
• Provide a reservoir of solar matter for 21st century science to be archived in the manner as the lunar samples.

Notice that the Genesis mission science objectives refer back to the composition of the sun, not that of the solar wind. Scientists want a sample of our sun because a preponderance of evidence suggests that the outer layer of the sun preserves the composition of our early solar nebula. Therefore, knowing the exact elemental and isotopic composition of the outer layer of our sun is effectively the same as knowing the elemental and isotopic composition of our nebula. We could then use that data to model how planets and other solar-system objects formed and then extend those results to understanding stellar evolution and the formation of solar systems elsewhere in the universe.

Clearly the ideal scientific option would be to send a spacecraft to the sun and grab some solar plasma; however, obtaining solar matter is not that straightforward because of the intense heat (millions of degrees kelvin ) of the Sun’s superheated gases as well as the dynamic electromagnetic environment of the corona, whose flares regularly interfere with the electronics of distant spacecraft. Luckily, the sun continuously sheds bits of its outer layer in the form of solar wind. Even better luck, data (prior to Genesis) suggests that the rock-forming elements are thought to maintain their relative proportions throughout the process of solar wind formation.

Accordingly, in order to practically meet the mission science objectives, the Genesis spacecraft was designed to collect solar wind ions and bring them back to Earth for analysis.^[7] Genesis carried a number of different solar-wind collectors, all of which passively collected solar wind; that is, the collectors sat in space facing the sun, while the ions in the solar-wind crashed into them at speeds over 200 km/sec and, on impact, buried themselves in the surface of the collectors. This passive collection is a process similar to that used by the semi-conductor industry to make certain types of devices, and a simulation of the process is given by the free-access program SRIM.^[8]

Most of the Genesis collectors continuously sampled all of the solar wind the spacecraft encountered (aka ‘bulk solar wind’). However, the spacecraft also carried three arrays of collectors which were deployed when specific “regimes” (fast, slow,coronal mass ejections) of solar wind were encountered, as determined by the electron- and ion- monitors on board.^[9] These deployable collector arrays were designed to provide data to test the hypothesis that the rock-forming elements keep their relative proportions throughout the processes forming solar wind.

There was a third, very important type of collector on Genesis: the concentrator. The concentrator collected bulk solar wind, but was discriminating in that it electrostatically repelled hydrogen and had enough voltage that it focused the light solar wind elements (e.g., C, O, N, S) onto a small target, concentrating those ions by a factor of ~20. This concentrator was the electrostatic equivalent of using a parabolic mirror from a telescope to cook a hot dog, and somewhat like using a magnifying glass to start a fire. The objective of the concentrator was to bring back a sample with enhanced amounts of solar wind ions to make it possible for analysts to precisely measure the isotopes of the light elements.^[10]

[edit] Operation

[edit] Mission profile

The launch of Genesis

Genesis was a Discovery-class mission of the NASA Jet Propulsion Laboratory (JPL) at the California Institute of Technology (Caltech). The spacecraft was designed and built by Lockheed Martin Space Systems. According to NASA, the total cost of Genesis was $264 million.

Genesis mission trajectory and flight plan

NASA launched the craft on a Delta II 7326 rocket on August 8, 2001 at 16:13:40 UTC from Cape Canaveral. Following launch, Genesis cruised to the Earth L₁ then performed a Lissajous orbit insertion maneuver, entering an elliptical orbit about L₁ on November 16, 2001. Genesis exposed its collector arrays to pick up solar wind particles expelled from the Sun on December 3, 2001. The collection process ended after 850 days, on April 1, 2004, with the spacecraft completing five halo loops around L₁. Genesis began its return to Earth on April 22, 2004. The return phase included an orbital detour toward the Earth L₂ so that the craft could be recovered during the daytime, as a direct approach precluded this possibility. After completing one halo loop about L₂, then returned to Earth for a planned September 8, 2004 recovery.^[11]

[edit] Recovery phase (planned)

The planned mid-air retrieval was extensively rehearsed

Following completion of the collection phase, the collector arrays were stowed in a sample return capsule, and the spacecraft returned to Earth. As the capsule was approaching Earth and at the first stages of re-entry, all appeared well.

A normal parachute landing might have damaged the delicate samples, so the mission design called for a mid-air retrieval of the sample return capsule. About 33 km above the ground, a drogue parachute was planned to be deployed to slow descent. Then, at a height of 6.7 km, a large parafoil was to be deployed to slow descent further and leave the capsule in stable flight. A helicopter, with a second helicopter as a backup, was then to attempt to catch the capsule by its parachute on the end of a 5 meter hook. Once retrieved, the capsule would have been soft-landed.

[edit] Recovery phase (actual)

The sample return capsule entered Earth's atmosphere at 16:55 UTC September 8, 2004 over northern Oregon with a velocity of approximately 11.04 km/s (24,706 mph).^[11] Due to a design flaw in a deceleration sensor,^[12] parachute deployment was never triggered, and the spacecraft descended slowed only by its own air resistance. The planned mid-air retrieval could not be carried out. The spacecraft crashed into the desert floor of the Dugway Proving Ground in Tooele County, Utah at about 86 m/s (311 km/h; 193 mph).

The Genesis capsule tumbles to Earth moments before it crashes

The sample return capsule crashed into the Utah desert floor, breaking open the capsule. The capsule is about 1.5 m (4.9 ft) in diameter and has a mass of 275 kg (600 lb)

The capsule broke open on impact, and part of the inner sample capsule was also breached. The damage was less severe than might have been expected given its velocity; it was to some extent cushioned by falling into fairly soft muddy ground.

[edit] Sample extraction & results

Unfired pyrotechnic devices in the parachute deployment system and toxic gases from the batteries delayed the recovery team’s approach to the crash site. Once all was made safe, the damaged sample-return capsule was secured and moved to a clean room for inspection; simultaneously a crew of trained personnel scoured the site for collector fragments and sampled the local desert soil to archive as a reference by which to identify possible contaminants in the future. Recovery efforts by Genesis team members at the Utah Test and Training range – which included inspecting, cataloging and packaging various collectors -- took four weeks.^[13]

Initial investigations showed that some wafers had crumbled to dust on impact, but others were largely intact. Desert dirt entered the capsule, but not liquid water. Because the solar wind particles are expected to be embedded in the wafers, whereas the contaminating dirt is likely just to lie on the surface, it may be possible to separate the dirt from the samples.

The analysis team was hopeful of being able to extract some useful data from the capsule. Roger Wiens, of the Los Alamos National Laboratory stated on September 10, 2004 that because much of the inner canister was still intact, and despite serious contamination, "We should be able to meet many, if not all, of our primary science goals". On September 21, 2004 the extraction was said to be going well, with wafer fragments beginning to be extracted from the science canister. NASA announced on January 27, 2005, that a first sample piece of an aluminum wafer was sent to scientists at Washington University in St. Louis for analysis.^[14]

On April 20, 2005, NASA announced that scientists at the Johnson Space Center in Houston had removed the four solar-wind collectors from an instrument called the concentrator and found them in excellent shape. The concentrator's targets collected solar-oxygen ions during the mission and will be analyzed to measure solar-oxygen isotopic composition, the highest-priority measurement objective for Genesis.^[15]

Confirming the integrity of the wafers and the recovery process, on October 18, 2007, the scientists at Washington University in St. Louis published detailed neon and argon isotope fractionation findings.^[16] Argon and neon isotopes in samples of three types of solar wind (fast, slow, and coronal mass ejections from the Sun’s surface) were captured and quantified. The findings effectively discount some theoretical models of stellar genesis.^{[clarification needed]} This much more precise data complements knowledge gained from earlier lunar argon measurements.

It was announced by Kevin McKeegan on March 10, 2008 that analysis of a silicon wafer has shown that the Sun has a higher proportion of oxygen-16 than does the Earth. The measurement was made after the upper 20 nm of the wafer was removed with a beam of cesium ions. This implies that an unknown process depleted oxygen-16 from the Sun's disk of protoplanetary material prior to the coalescence of dust grains that formed the Earth.^[3]

Ironically, it was not terrestrial desert soil introduced in the crash that proved most difficult to deal with during the sample analysis process but the craft's own flight-introduced compounds such as lubricants and craft-building materials.^[17]

[edit] Fate of spacecraft bus

After releasing the sample return capsule on September 8, 2004, the spacecraft bus headed back toward the vicinity of the Earth-Sun Lagrange Point (L1). A trajectory correction maneuver was performed on November 6, 2004 to allow it eventually to leave L1 if the bus was not used for an extended mission. Final commands were radiated on December 2, 2004,^[18] to put Genesis into hibernation. While in this "safe" mode, it will continue transmitting health and safety information, autonomously pointing its solar arrays toward the Sun. The spacecraft bus left L1 around February 1, 2005, staying in a heliocentric orbit leading the Earth.^[19]

[edit] Mishap Investigation Board

Genesis staff have started sorting through the debris from the sample canister.

A 16-member NASA Genesis Mishap Investigation Board (MIB) was quickly formed, including experts on pyrotechnics, avionics, and other relevant specialties. The MIB started its work on September 10, 2004 when it arrived at Dugway Proving Ground. It determined that all scientific hardware meant to be curated by the Johnson Space Center could be released and were not needed for the work of the board. Both JPL and Lockheed Martin began to prepare flight data and other records for the MIB.

It was announced on September 23, 2004 that the capsule, having had the science material extracted, would be moved to the Lockheed Martin Space Systems facility near Denver, Colorado, for MIB use.

A first possible root cause of the failed deployment of the parachutes was announced in an October 14 press release. Lockheed Martin had built the system with an acceleration sensor's internal mechanisms wrongly oriented, and design reviews had not caught the mistake. The intended design was to make an electrical contact inside the sensor at 3 g (29 m/s²), maintaining it through the maximum expected 30 g (290 m/s²), and breaking the contact again at 3 g to start the parachute release sequence. Instead, no contact was ever made.^[20]

The same general parachute concept was also used on the Stardust comet sample return spacecraft, which landed successfully in 2006; but that system was said not to have Genesis's flaw.

Closeup of the type of accelerometer that was installed backwards, alongside a pencil for scale (lower section) with a view of the spacecraft capsule and bus.

The chair of the NASA investigation board, Michael Ryschkewitsch, noted that none of the stringent review procedures at NASA had picked up a mistake, saying, "It would be very easy to mix this up".

This mishap is strikingly similar to the original event that inspired Edward A. Murphy, Jr. to formulate the now-famous Murphy's Law: an accelerometer installed backwards.^[21] On January 6, 2006, Ryschkewitsch revealed that a pre-test procedure on the craft was skipped by Lockheed Martin, and added that the test could have easily detected the problem.^[22]

[edit] References

[edit] External links

• "Genesis Mission Home Page". JPL. http://genesismission.jpl.nasa.gov/. Retrieved 2008-05-21. 
• Genesis Mission Profile by NASA's Solar System Exploration
• "Impact video" (QuickTime movie). http://anon.nasa-global.speedera.net/anon.nasa-global/genesis/genesis.mov. Retrieved 2006-04-20. 
• Associated Press (23 September 2004). "Genesis Capsule to Be Sent to Colorado". SPACE.com. http://www.space.com/scienceastronomy/genesis_lockheed_040923.html. Retrieved 2006-04-24. 
• Pegg Jr., Ed (September 7, 2004). "Manifolds in the Genesis mission". Math Games. Mathematical Association of America. http://www.maa.org/editorial/mathgames/mathgames_09_07_04.html. Retrieved 2006-04-24. 
• "MegaSIMS Home Page". UCLA. http://megasims.ess.ucla.edu/. Retrieved 2008-12-05. 

v • d • e Solar space observatory missions Current Pioneer 6, 7, 8, and 9 · GGS WIND · SOHO · ACE · TRACE · RHESSI · Hinode · STEREO · Koronas-Foton Spaceflight portal Completed Helios probes · ISEE 1–3 · SolarMax · Ulysses · Yohkoh · Pioneer 5 · Orbiting Solar Observatory Sample return Genesis Future Solar Dynamics Observatory · PICARD · Solar Orbiter · Solar Probe · Solar Sentinels Cancelled Pioneer H