MAGELLAN (Micrometeorite Collector)

The MAGELLAN was a balloon-borne experiment designed to collect large cosmic dust particles, specifically targeting solid particles from two postulated extraterrestrial origins: cosmic dust particles that had partially ablated while penetrating the atmosphere, and fragments of much larger particles or bodies that disintegrated upon entering the atmosphere. It was a collaborative effort between the National Research Council of Canada (NRCC) and the Dudley Observatory in Albany, New York. As the experiment was designed to be carried by superpressure balloons capable of long-duration flights that would circle the world many times, it was named after the Portuguese explorer Ferdinand Magellan who lead the first circumnavigation of Earth in history.

In the image at left we can see one of the few images known of the system. The heart of MAGELLAN was a large funnel measuring 7.2 meters in diameter, providing a collection area of 40 square meters. This funnel was fabricated from 12-micrometer-thick mylar that was lightly coated with aluminum to reduce static charge buildup. The designers carefully engineered the gore pattern so that all seams overlapped essentially downward to minimize particle trapping inside the funnel. After some laboratory tests a 60-degree funnel apex angle was considered optimal yielding recovery rates of 90-100 %.

The funnel required a sophisticated deployment mechanism since it needed to remain collapsed during ascent and deploy only at float altitude to facilitate launch, reduce contamination, and prevent destruction during atmospheric passage. The researchers initially developed a mechanism consisting of a ten-segment toroid fabricated from 150-micrometer-thick mylar-aluminum lamination, with segments that were pleated and inflated on command from a small CO2 cylinder. However, the possibility of faulty deployment due to unbalanced forces in the load lines became evident during the first launch, necessitating the development of a more reliable system. The second mechanism functioned essentially as an inverted umbrella with gravity-operated deployment. To overcome the configuration's tendency to remain closed, the designers incorporated a pulley system with a mechanical advantage of 4 into the stem. The deployment was achieved by sliding a conically-shaped open structure toward the top of the stem, with the deployment rate governed by an escapement mechanism housed in a sealed square enclosure at the stem's top.

At the apex of the collecting funnel, a sample collector was attached that could accommodate three sampling pans. These pans could be sequentially swung into position below the funnel, exposing clean collection surfaces that could then be sealed after exposure and ejected to make room for subsequent sampling pans. The identical collection units were mounted on three of the four sides of a square frame that housed a small stainless steel funnel forming the apex of the collecting system. This small funnel guided particles to a 1-centimeter diameter hole in the bottom face of the frame, which remained open during launch, funnel deployment, and a short stabilization period at float altitude to allow contaminant particles to fall through the system.

Each collecting pan contained two collection surfaces: a smaller disc lightly coated with mineral oil served as the primary surface, while a larger disc positioned above it collected bouncing particles. The pan assembly included a cover and a slider moved by a bellows actuator, with a bar magnet cemented to the slider's edge that actuated a reed switch when moved to indicate pan sealing. The collection process was terminated by firing actuators to seal the pan, after which the sampling unit was removed by two cutters that released a compressed spring while keeping the removed unit attached to the payload via electrical cable.

The experiment utilized pyrotechnic devices throughout the system because of their reliability, with redundancy provided by using two bellows actuators to seal each pan and two cutters to eject the units. Each cutter included two filaments for additional redundancy. The system was designed to operate reliably at ambient temperatures as low as -75°C, with the low-temperature lubrication problem resolved by fabricating critical components from impact-resistant, self-lubricating plastic, while silicone rubber was used for all seals and aluminum for other parts to minimize weight. The complete collector weighed 4 kilograms.

Balloon launched on: 5/6/1974 at  
Launch site: Columbia Scientific Balloon Facility, Palestine, Texas, US  
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon Raven 14.158 m3 (25.40 Microns - X-124)
Flight identification number: 823P
End of flight (L for landing time, W for last contact, otherwise termination time): 5/6/1974
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): F 19 h 55 m
Payload weight: 190 kgs.

• Magellan collections of large cosmic dust particles In: Elsässer, H., Fechting, H. (eds) Interplanetary Dust and Zodiacal Light. Lecture Notes in Physics, vol 48. Springer, Berlin, Heidelberg
• Magellan collections of large cosmic dust particles Lecture Notes in Physics Volume 48, 1976, pp 284-288
• Magellan: A balloon-borne collection technique for large cosmic dust particles Canadian Journal of Physics, Volume 54, Number 3, February 1976
• National Scientific Balloon Facility Annual Report FY 1974 National Center for Atmospheric Research, December 1974
• Tapered Element Oscillating Microbalance (TEOM) for Magellan Balloon Dudley Observatory archives