ASIM: Climate and giant lightning discharges to be studied from the International Space Station - DTU Space
Mounted on the ISS external facilities of the Columbus module, the Atmosphere-Space Interactions Monitor (ASIM) will study giant electrical discharges (lightning) in the high-altitude atmosphere above thunderstorms.
DTU Space provides the scientific management for this project and is responsible for delivering a package of instruments (2 cameras, 3 photometers and one X- and gamma-ray detector) which will be mounted on the International Space Station.
ASIM has a number of cameras, specially designed for the International Space Station, that will observe the Earth's atmosphere. ASIM will give new insights into climate processes that will improve climate models by quantifying the effect of electrical and chemical processes at the atmosphere/space boundary.
Introduction | Research | Technology | Mission | Partners |
Introduction
The Atmosphere-Space Interactions Monitor (ASIM) will study the Earth's atmosphere as one system, from the surface of the Earth to the edge of space. The atmosphere is the thin layer that covers the planet's crust, and protects life as we journey through space.
ASIM will observe extreme thunderstorms, water vapor, clouds, aerosols and their interplay in the atmosphere.
The mission is realized through the European Space Agency (ESA). The National Space Institute of the Danish Technical University (DTU Space) provides the scientific leadership, and the Danish company, Terma, the technical leadership. Other major partners include the University of Valencia in Spain, and the University of Bergen in Norway, who are both involved in the development of the instruments.
DTU Space provides the scientific management for this project and is responsible for delivering a package of instruments (2 cameras, 3 photometers and one X- and gamma-ray detector) which will be mounted on the Columbus module of the International Space Station,
ASIM consists of a number of cameras,specially designed for the International Space Station, that will observe the Earth's atmosphere. ASIM will give new insights into atmospheric processes that will improve climate models.
Research
ASIM research has three themes: Climate processes, the interplay of the atmosphere with the Earth's surface and changes to the atmosphere from space processes.
Click on the read headings to read more about each theme
- Thunderstorms
- Electrical discharges in the stratosphere and mesosphere
- X- and gamma-radiation from thunderstorms
- Water vapor transport
- Cloud nucleation
- Gravity waves
- Noctilucent clouds
- The dynamics of the upper atmosphere
Earth's surface and the atmosphere
- Hurricanes
- Dust storms
- Volcanoes
- Forest fires
Interactions of space processes with the atmosphere
- Comets and meteors
- NO from solar radiation
- Thunderstorm interactions with the ionosphere and magnetosphere
- Aurora
Measurements from other satellites and instrumentation on the ground and on aircraft or balloons will also be used to complement the ASIM data.
Technology
The International Space Station
The International Space Station (ISS) orbits the earth at an altitude of about 400 km. It continues to be expanded with additional modules and facilities, including the Columbus module delivered by the European Space Agency (ESA), launched in 2008. Denmark has delivered hardware and software to the ISS and has conducted physiological tests on astronauts to understand the functioning of the human blood pressure system under weightlessness. A Danish astronaut, Andreas Mogensen, will be sent to the ISS for a 10-day mission in September 2015.
The ISS is in the lowest possible permanent orbit. Altitude is maintained by the spaceships docked at the station. They give the ISS a boost with their engines, lifting the altitude. If this is not done, the ISS will loose altitude because of air drag, and would burn up within 2 years.
The orbital plane is 51.6 degrees relative to the equatorial plane. This allows for observations over the main thunderstorm regions of the earth. At the same time, the ISS reaches sufficiently high latitudes to study energetic particle precipitation and aurora powered by violent storms on the Sun.
Columbus
ASIM scientific instruments include 6 cameras, 3 photometers and one X- and gamma-ray detector. Four of the cameras, with 4 companion photometers are directed forward towards the horizon (ram, limb). While the two remaining cameras, two photometers and the X- and gamma-ray detectors are directed downwards (nadir) towards the Earth's surface. The cameras and photometers constitute the Modular Multispectral Imaging Array (MMIA). Each module includes two cameras and two photometers, such that there are 3 MMIA modules in all, two pointing forward and one downward. The MMIA instruments observe in different optical spectral bands. The two MMIA modules which are directed forward towards the horizon observe thunderstorms from the side, where it is possible to identify directly the effects of lightning on the atmosphere as a function of altitude.
The X- and gamma-ray detector is called the Modular X- and Gamma-Ray Sensor (MXGS). X- and gamma-rays are strongly absorbed in the atmosphere. This is why the detector points directly downwards, so that a minimum of atmosphere lies between the detector and the thunderstorms within its field of view. Most of the atmosphere is below the altitude where giant lightning and terrestrial gamma-ray flashes are generated. Therefore, space is particularly well-suited to observe these phenomena in the spectral range reaching from gamma-rays to UV, which is difficult to observe from the ground. ASIM cantherefore measure in these spectral bands (colors) without atmospheric absorption.
The Optical Cameras
| Field-of-view |
Forward: 20x20 degrees; Downward: 56 degrees |
| Pixels | 1024x1024 |
| Spatial resolution | Forward: 300-600 m; Downward: 300-400 m |
| Bits/pixel | 12 |
| Time resolution | 80 ms |
| Spectral bands |
Forward: 337nm; 391.4nm; 650-800nm;762nm Downward: 337nm; 650-777nm |
The cameras are sufficiently light-sensitive without the use of intensifiers. This is made possible by a new CCD, with on-chip amplification. This means that the CCD will not be damaged if the cameras view the sun or the moon by mistake. Because the cameras are so light-sensitive, they can only make scientific observations during the night, or at sunrise and sunset, as seen from the space station.
The Optical Photometers
Photometers are used to measure rapid time variations, which cannot be done by imaging cameras. They view the exact same region as the cameras but measure only the total photon flux from the entire field-of-view. However, unlike cameras, they measure with very fine time resolution.
| Field-of-view |
Forward: 20x20 degrees; Downward: 80x80 degrees |
| Time resolution | 10 microseconds |
| Spectral bands |
Downward: 180-300nm, 337nm, 777nm |
The X- and gamma-ray detector
The detector plane is made of semiconductor crystals that are sensitive to photons hitting the crystals. The detector measures each photon and determines its energy and time of arrival. This detector principle is relatively new and allows for a simpler design than used for instruments in the past.
| Energy range |
7-500 keV |
| Energy resolution | <10% |
| Detector area. |
1032 cm2 |
The Mission
The Launch
ASIM is expected to be launched to the International Space Station (ISS) in July 2016, from where it will observe the atmosphere for 2 years. ASIM will be carried by the HTV (Heavy Transfer Vehicle), which is a cargo vessel able to carry up to 6 tons of supplies for the space station. The HTV is launched by a rocket, but has its own propulsion system allowing it to maneuver to the space station for docking.
Operations
When ASIM is mounted on the external pallets of Columbus, the instruments will be turned on by commands sent from the control center outside Odense, Denmark. The first operational period is used to check if the instruments have survived the violent vibrations experienced during launch. This phase is called the 'commissioning phase'.
If the instruments work properly, the scientific observational phase can begin. The X- and Gamma-ray sensor is on continuously, except during passage of the South Atlantic Anomaly (SAA), where the earth's magnetic field is weak, allowing considerable fluxes of energetic particles to reach the space station. The optical instruments are on during the night time and sunrise/sunset, as seen from the space station. The instruments automatically capture brief flashes of lightning activity as they occur. Certain observations over high acitvity areas, such as the Mediterranean region, are executed as, pre-planned, time-tagged commands, sent in advance to ASIM from the control centre.
Partners
The Technical Consortium
Design and development of the ASIM payload is being done by an international consortium:
The Scientific Team
The ASIM project is advised by an 'ASIM Facility Science Team' who include:
- Torsten Neubert, National Space Institute, DTU (chairman)
- Victor Reglero, Universidad de Valencia, Spain
- Nikolai Østgaard, Universitetet i Bergen, Norway
- Elisabeth Blanc, Commisariat à l’Énergie Atomique, France
Further consultations involve the 'ASIM International Science Team'. To date, the science team includes 80 research groups from 29 countries. In Denmark the following are members:
- National Space Institute - Danish Technical University
- Danish Meteorological Institute
- Niels Bohr Institute, University of Copenhagen
- Aalborg University