Collecting Stardust

On January 2, 2004, NASA's Stardust Mission flew through the tail of the Comet Wild 2 with a series of aerogel collectors exposed to gather extraterrestrial materials for scientific investigation upon return to Earth. And now, with the Stardust Mission scheduled to land this month, a new clean-room laboratory and high-precision scanning system is set to process, scan, and store the samples after the preliminary science investigation team finishes its work.

Thomas See, a planetary geologist and principal scientist on the Engineering & Science Contract (ESC) at the Johnson Space Center, says that the recent Genesis and Stardust missions are the first physical, extraterrestrial, sample return missions since the last Apollo flight in 1972. See says that the Stardust Mission is especially important because the common theory with cometary particles is that they represent leftovers from the formation of the solar system.

"Our goal during the preliminary examination phase is to extract six to 12 particles and provide mineralogical, chemical, and isotopic documentation for scientists around the world," See says. The scientific community will use that information to make intelligent sample requests for all types of detailed research studies.

New-laboratory setup

In preparation for the return of the Stardust (http://stardust.jpl.nasa.gov), NASA has built a new laboratory area and Class 100 clean room at the

A new high-precision scanning system is set to process cometary particles collected when NASA's Stardust Mission returns to earth this month.

Johnson Space Center where researchers will examine samples, which will be stored long-term. ARES (Astromaterials Research and Exploration Sciences) is responsible for maintaining and distributing samples that the United States has in its possession to qualified scientists around the world.

A new scanning system in the lab can handle samples as large as 3 ft in diameter and weighing 50 lbs. Because standard automated stages used in medical applications offered excellent precision but inadequate stage area (typically, 4 × 5 inches), NASA worked with Texonics (www.texonics.com), a systems integrator in Houston, to build a custom system because no commercially available systems met the lab requirements.

One unusual requirement was the desire for the scanning system to operate in both a horizontal and vertical configuration. Multiple configurations make it easier to handle bigger objects and provide contamination control, because the Stardust samples are critically important and researchers want to avoid mounting equipment over the samples. The vertical system orientation also allows scientists to use transmitted light with Stardust's translucent collectors to more clearly see tracks and particles embedded into the material.

System configuration & operation

The system has three axes (X, Y, and Z) and uses positioning slides from Parker Daedal (www.parkermotion.com) to provide close to one micron repeatability over 30 inches of travel. A Newport optical bench with air-filled or nitrogen-filled legs dampens any vibrations.

Two 24-inch slides mounted on a 0.5-inch aluminum plate enable scientists to use the system in a vertical or horizontal configuration. The system also has 1-inch centered holes on the optical bearing, so users can precisely position it on the bench. A 4-inch iron H-beam on two 4-inch-diameter poles provides an optical bridge over the scanning system for mounting the Leica MZ16A microscope, which provides a motorized zoom and Z-axis microscope.

Scientists review collector grid from Stardust Mission- more than 60 cells holding a 2 x 4-cm aerogel tile to capture extraterrestrial particles from the tail of Comet Wild 2.

Matt Batchelor of Meyer Instruments Inc. (www.meyerinst.com), developed the custom application program that controls the positioning system, microscope, and ImagePro image-acquisition software. The Windows-based application program operates the system, sets up small or large areas for investigation, and automatically images areas at any magnification that the system can handle. The system stores the images and then moves on to the next one. "All we need to do is define three points on a plane, and the system will automatically image the area," See says.

When the Stardust Mission returns, scientists will use the system to scan the aerogel collectors—a grid a little larger than the head of a tennis racket divided into more than 60 cells with each cell holding a 2 × 4-cm aerogel tile. Each tile will be scanned at high resolution to document penetrations and impact locations for the particles.

"Once that is complete, we will choose six aerogel collector tiles and extract them from the collector and try to recover the actual impact particles," See says. "Aerogel is a super under-dense medium that decelerates particles over a short distance without imparting too much pressure, shock, or heat into the particle. The goal is to decelerate and capture the particles in as pristine condition as is possible."

Moving ahead

Until the Stardust Mission returns, scientists are busy doing lighting tests to determine the best system configuration for analyzing the samples. See says that they know that acoustic sensors in the system impacted Stardust collectors several thousand times. "We're confident we will come home with enough material to keep us busy for a long time," he says.

For more info on the Parker Daedal positioning slides used in this application, go to:http://rbi.ims.ca/4911-523.