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The ASIM Observatory

The European Space Agency selected Terma to head the Atmosphere-Space Interactions Monitor, a European space program with the objective to take measurements and make observations from the International Space Station. The observatory will measure high altitude lightning discharged from thunderclouds.


Introduction

The Atmosphere-Space Interactions Monitor (ASIM) project was originally initiated from Denmark and carried through as a study headed by DTU Space. In the industrial phase, Terma was responsible for the specifications and design. In 2010, ESA selected Terma to head the program with expected launch in 2016. This is the first time, Terma is main contractor of space equipment on a program for the European space organization ESA, and at the same time, it is the largest Danish commitment in space since the Ørsted satellite.

ASIM is an observatory to be placed on the exterior of the ISS. It will measure high altitude lightning that is discharged from thunderclouds, stretching up to the ionosphere at altitudes of 90-100 km. These formations of lightning are known as "red sprites", "blue jets", and "elves". In addition, the ASIM project will study the discharges observed in the form of energetic bursts of X-rays and gamma rays, likewise discharged from violent lightning.  

The video below has been produced by DTU Space:

 


Benefits

ASIM will address a variety of important scientific and technological aspects which will include: 

  • Understanding of the processes involved in thunderstorm initiated electrical discharges
  • Understanding their impact on atmospheric processes and possible links to climate determining factors
  • Development of new technologies with spin-off into terrestrial applications for advanced process control and optical instrumentation
  • Demonstration of the fruitful utilization of the collaborative investments in the International Space Station. 

These discharges are linked to violent storms in the tropics and inject water vapour, NOx, and other greenhouse gases into the stratosphere where they become part of the climate moderators.

ASIM will study these effects, as well as the electrical influence on the ionosphere and the atmospheric interactions with the particle radiation from the Sun. Both of which also have a direct bearing on the Earth's climate.

In science terms, the optical events are referred to as Transient Luminous Events (TLEs), and the X- and gamma ray events as Terrestrial Gamma Flashes (TGFs).

Flying the ASIM instrument package on the ISS provides a unique opportunity for systematic monitoring of these phenomena on a global scale. Furthermore, the advanced detector technology to be used for ASIM will have spin-off into a range of important terrestrial applications. 

The video below has been produced by DTU Space, Illustrator Jan Erik Rasmussen

 


Functionality

ASIM consists of two optical cameras, 3 photometers, and one large X- and gamma ray detector. The instruments will be installed on the Columbus External Pallet to be mounted on the exterior of the Columbus module, housing ESA's laboratory on the ISS.

The optical assembly referred to as the Modular Multi-spectral Imaging Array (MMIA) comprises two optical narrow band cameras and three photometers with related optical and signal processing capabilities, including autonomous event detection algorithms to identify and prioritize events for download to Earth. 

The MMIA instrument will be combined with the X- and gamma ray detectors into the Nadir Viewing Assembly looking directly down on top of thunderstorms above the Earth.

The Modular X- and Gamma ray Sensor module (MXGS) is designed to detect radiation from Terrestrial Gamma Flashes (TGF) and from lightning induced electron precipitation. The detector is built around a Bismuth Germanium as well as Cadmium Zinc Telluride semiconductor detection plane of 32 cm x 32 cm with possible imaging capabilities.

Fast electronic circuitry used in the MXGS will provide time history and spectra over the course of the expected lifetime of 1-5 ms for each TGF. Also, a TGF burst trigger signal is passed to the adjacent MMIA module (and visa versa) for synchronization of the two types of observation.

The project has been a Danish initiative, from the very start, headed in the initial phase by the DTU Space, National Space Institute, with participation of the University of Valencia and the University of Bergen. The development phase of ASIM has an estimate time span of 3 ½ years leading up to the launch and operational phases. ASIM is scheduled to be ready for launch by the end of 2015 and will be launched by SpaceX with the Falcon-9 lift rocket carrying the Dragon Transfer Vehicle to the International Space Station.

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