Micro system from Chalmers improves measurements in space

Scientists at Chalmers MC2 have developed a new type of microshutter with extremely short opening times. The microshutters are an integral part of the ion sensor PRIMA that will measure particles in space onboard the Swedish-led satellite project PRISMA.

PRISMA was launched into Earth orbit on June 15. The PRIMA sensor project is a collaborative venture between the Swedish Institute of Space Physics (IRF) in Kiruna and Chalmers.

Charged particles from the Sun travel throughout the solar system using the solar wind. In their interaction with the Earth's magnetic field and atmosphere, phenomena such as the Northern Lights are created. To understand the various processes that take place it is important to be able to measure and separate atoms, such as hydrogen and oxygen. This is done by measuring their mass.

Time-of-flight (TOF) is a technique commonly used in space sensors to measure the velocity of particles and in doing so determine their mass. The velocity is determined by measuring the time it takes for a particle to travel a known distance inside the sensor. The start signal comes from secondary electrons created as the particle flies though a thin foil or grazes a surface and the stop signal comes from when the particle impacts a detector at a known distance from the foil.

The problem with TOF instruments used today is that the particles being measured lose velocity as they traverse the foil. This also sets a lower limit on the energy of neutral atoms that are detectable.

- If, instead of a foil, a microshutter is used to generate the start signal it is possible to increase the sensitivity of the measurements and make detection of a low-energy neutral atom possible, says project leader Klas Brinkfeldt.
The shutter is mechanical, in principal a micro-sliding door that opens and shuts within nanoseconds, and it is manufactured from monochrystalline silicon.

Peter Enoksson is Professor at MC2 at Chalmers:

- It is an amazing mechanical material - stronger that steel, lighter than aluminum and the basis of today's microelectronics. The microshutters were made in the Chalmers Nanofabrication Laboratory, which is a first-rate clean room facility.

Klas Brinkfeldt stresses that this is a textbook example where miniaturization and microtechnology are necessary:

- The microshutters not only produce faster opening times, which improves the resolution of the measurements, they also require less power, take up less volume, and have less mass than larger shutter systems. These are very important characteristics when it comes to space-based instrumentation.

PRISMA is a technology mission consisting of two satellites and is aimed primarily at demonstrating different sensor technologies and guidance/navigation strategies for rendezvous and formation flying in space.

The technologies onboard PRISMA have been developed in Sweden, with contributions from Germany, Denmark and France. The project is funded by the Swedish National Space Board with support from the French and German space agencies. The Swedish Space Corporation is the prime contractor for the satellites.

Contacts

Dr. Klas Brinkfeldt, Swerea IVF AB, +44 (0)707-80 60 82 Professor Peter Enoksson, Chalmers, +44 (0)31-772 1868 Professor Stas Barabash, IRF, Kiruna +44 (0)980-791 22