Digital Ion Drift Meter (DIDM) instruments are designed to measure the velocity vectors of ambient ions at a spacecraft's location. Measurements of ion density and temperature are also provided. The local electrical field strength can be obtained via the relationship between electrical field, ion drift velocity and the measured magnetic field provided by on-board magnetometer.
The DIDM-1000 series is comprised of two sensors mounted directly onto the electronics housing. The sensors can be pointed to obtain optimal orientation for instrument location and ion species of interest. Easy accommodation of different types of spacecraft interfaces is accomplished by having a dedicated interface card within the instrument.
Incident ions are focused onto a Micro-Channel Plate (MCP) detector, in a manner similar to the operation of a pinhole camera. Trajectories are determined from the impact location of the MCP output onto a wedge and strip anode. The anode provides the azimuth and elevation components of the incident ion's trajectory, which correspond to the velocity components as well. The normal velocity component is determined separately, by the Retarding Potential Analyzer feature of the instrument.
The instrument is made of state-of-the-art components, detector technology, data processing capability and measurement resolution. It is designed to achieve at least two orders of magnitude improvement over analog instruments of the same type.
| Size | 6"x5"x4.5" (150mmx128mmx112mm) |
| Weight | 5 lbs (2.3 kg) |
| Power | 5 Watts from a 28 Volt supply |
DIDM on the CHAMP Spacecraft
Revised on February 7, 2001
