Astrid 2

Astrid 2 [SSC]

Astrid-2 is Sweden's second scientific microsatellite developed by Swedish Space Corporation's Space Systems Division in Solna, Sweden. Astrid-2 was launched piggyback on a Kosmos-3M rocket from Plesetsk on 10 December 1998. On 24 July 1999 the contact with the satellite was lost during a passage. Several attempts to re-establish the contact have been made without any results. During the 7.5 months in orbit, Astrid-2 delivered a large quantity of data to the scientists.

The scientific mission is:

• High resolution E-field and B-field measurements in the auroral region.
• Electron density measurements.
• High resolution measurements of the electron and ion distribution functions
• Ultraviolet auroral imaging and atmospheric UV-absorption measurements

The scientific payload consists of:

• EMMA (Electrical and Magnetic field Monitoring of the Aurora) is a comprehensive scientific experiment measuring both electrical and magnetic fields. EMMA is logically divided into three parts, EMMA system unit, EMMA E-field unit and EMMA B-field unit. The EMMA system unit controls the experiment units, buffers scientific and housekeeping data and communicates with the satellite system unit. Data can be buffered during several orbits and dumped to ground whenever the satellite has an ground connection. EMMA system unit do also control LINDA.
• LINDA (Langmuir INterferometer and Density experiment for Astrid-2) consists of two 10 mm diameter spherical probes mounted on two light weight booms. The booms are 0.61 m long and mounted on the outer tips of the solar panels giving a probe to probe separation distance of 2.9 meters. The scientific goal is to measure the fine structure of the plasma density irregularities down to 1 m scales and, by using two probes, distinguish between temporal and spatial effects. This will be achieved by using a high sampling rate (32 ksampl/s) and by using snapshot technique. The measured quantities are the plasma density derived from the probe current and the relative density variations derived from the variations in the probe current.
• MEDUSA (Miniaturized Electrostatic DUal-tophat Spherical Analyzer) is a combined electron and ion spectrometer. The instrument is provided jointly by the Southwest Research Institute, San Antonio, Texas, and the Swedish Institute of Space Physics, Kiruna Division. Electrons and ions with energies up to 18 keV.q will be measured simultanoesly, with a resolution of 16 energy sweeps per second for electrons, and 8 seconds for ions. Particles are measured in 16 sectors in the plane of acceptance, which is almost parallel to the satellite spin plane. MEDUSA includes a CPU for instrument control and data compression.
• PIA (Photometers for Imaging the Aurora) consists of two spin-scanning photometers (PIA-1/2) for auroral imaging and one sunward looking photometer (PIA-3) for atmospheric absorption measurements. PIA is provided jointly by the Max-Planck-Institut für Aeronomie, Lindau, Germany, and the Swedish Institute of Space Physics, Kiruna Division. PIA-1 and PIA-2 have four pixels each, and a focal width of 250 mm. PIA-3 is located under the sunward facing platform, and views the Sun in Lyman-alpha (121 nm) via a diffuse reflector. The photometers are sampled at 256 samples per second.