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Genesis (spacecraft)

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http://en.wikipedia.org/wiki/Genesis_(spacecraft)


In its collecting configuration, the Genesis spacecraft exposed collecting wafers to the solar wind. (Courtesy NASA/JPL-Caltech)
In its collecting configuration, the Genesis spacecraft exposed collecting wafers to the solar wind. (Courtesy NASA/JPL-Caltech)

The Genesis spacecraft was the first ever attempt to collect a sample of solar wind, and the first "sample return mission" to return 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 subsequent processing was able to isolate useful samples, and as of March 2008 all of the mission's major science objectives are expected to be achieved successfully.

Objective


A Genesis collector array consisting of a grid of ultra-pure wafers of silicon, gold, sapphire, diamond and other materials
A Genesis collector array consisting of a grid of ultra-pure wafers of silicon, gold, sapphire, diamond and other materials

The primary mission objective was to collect samples of neon and argon in order to determine the exact proportions of elements in the Sun which could hopefully answer questions about the make-up of stars, molecular clouds, galaxies, and the universe. Scientists have long had a solid theoretical basis on stellar evolution, but could only speculate on specifics. Also, because the Sun is made from the same molecular cloud that made the Earth, obtaining particles would also help see the material these molecular clouds are made from, helping to answer questions on the necessary conditions for life to exist.

Obtaining the solar matter was not straightforward. The corona, the closest that a craft could get to the Sun, burns at an intense 1-3 million kelvin, making a direct sample impossible for a craft of any known material. NASA scientists instead decided to use collector arrays to collect the solar wind. Genesis had three distinct collector arrays, with only one exposed at any time. The three arrays were each used to collect a different type of solar wind, with the exposure of the arrays controlled based on solar observations (such as a coronal mass ejection).

Each collector array consisted of a grid of ultra-pure wafers of silicon, gold, sapphire, diamond and other materials. The solar wind particles travel with such high speed that they would normally be obliterated upon a high-speed collision, but the special wafers have very low density. This low density enables the particles to be caught at high speed, analogous to throwing a marble into a ball pit; the marble glides around the much larger balls and air until it settles deep in the pit.

Operation

Launch and sample collection


The launch of Genesis
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.

NASA launched the craft on a Delta II 7326 rocket on August 8, 2001 at 16:13:40 UTC from Cape Canaveral. Genesis followed a complicated Interplanetary Transport Network trajectory to a chaotic Lissajous halo orbit at the L1 Lagrange point between the Earth and the Sun. From December 3, 2001 to April 1, 2004 it exposed collector arrays to pick up atoms of solar wind expelled from the Sun.

Sample retrieval


The planned mid-air retrieval was extensively rehearsed
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.


The Genesis capsule tumbles to Earth moments before it crashes
The Genesis capsule tumbles to Earth moments before it crashes

The sample return capsule entered Earth's atmosphere on September 8, 2004 while the remainder of the spacecraft was diverted into an irretrievable sunward orbit to avoid atmospheric entry. Due to a design flaw in a deceleration sensor, 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 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 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.

Sample extraction & results

The damaged capsule was moved to a clean room for analysis, and the unfired pyrotechnic devices made safe. 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.

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.

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. 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. 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.

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.

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, 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.

Mishap Investigation Board


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

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.

Shortly after the spacecraft crashed, it was pointed out that Colin Pillinger, part of the science team analysing the collected samples, was also the Principal Investigator for the ill-fated Beagle 2 mission to Mars. It had been suggested that the cause of Beagle 2's loss (which is as yet undetermined) might also have been due to a parachute failure. The determination of the cause of Genesis's parachute failure rules out any link between the two failures.


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.
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. 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.

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Published - July 2009














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