First Results From the SSJ5 Precipitating Particle Sensor on DMSP F16: Simultaneous Observation of KeV and MeV Particles During the 2003 Halloween Storms
Abstract
The first SSJ5 auroral electron and ion spectrometer was launched on the F16 spacecraft of the Defense Meteorological Satellite Program (DMSP) on 18 October 2003, and started providing data on 27 October 2003. This sensor replaces the highly successful SSJ4 series of particle spectrometers (ten SSJ4s launched between 1982 and 1999). The SSJ5 has mass 3.2 Kg, nominal power 1.4 W, and size 23 x 15 x 15 cm3. It is an electrostatic analyzer with triquadrisphere geometry, and a 90° x 4° field of view. The 90° zenith to horizon dimension is divided into six 15° angular sectors. Electron and ion counts at 19 energies, from 30 KeV to 30 eV, are measured each second, with a dwell time of 50 msec per energy channel. The instrument can be run in either of two formats. In Format A, particle counts from all six angular sectors are summed once per second. This emulates the temporal resolution of the SSJ4, which does not have angular zones. In Format B, particle counts from the six angular sectors are provided one zone at a time to provide enhanced pitch-angle resolution. In this format, the particle counts for each zone have been summed over the previous six seconds. The instrument has been run for extended time periods in both Format A and B. While Format B has reduced precision for determining features such as auroral boundary crossings, it is useful for characterizing the degree of anisotropy of the particle fluxes. The SSJ5 sensor was turned on in time to catch the Halloween storms of 2003, and provided an excellent data set. In addition to the expected 30 KeV - 30 eV particles that entered the instrument through its apertures and traveled along the intended triquadrisphere paths until they reached the microchannel plate (MCP) detectors, the data included MeV particles that are interpreted as having penetrated the side of the instrument. The SSJ5 MCP detectors are much more sensitive to these MeV particles than the SSJ4 channeltrons due to the larger sensitive area of the MCPs. SSJ5 data during and after the storms showed enhanced outer zone electron horns. SSJ5 data from the first several months of operation are compared with SSJ4 data from other DMSP spacecraft.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSMSH53A..03K
- Keywords:
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- 2716 Energetic particles;
- precipitating;
- 2788 Storms and substorms;
- 2794 Instruments and techniques