LANL Magnetospheric Plasma Analyzer (MPA) data for the days of Jan. 21, 2005 and Jan. 22, 2005.

From https://pwg.gsfc.nasa.gov/istp/collaborating/lanl_inst.html (or https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1990-095A-01): The Magnetospheric Plasma Analyzer (MPA) was designed to minimize weight, power, and volume while providing comprehensive measurements of plasma conditions. Similar instruments are on board all three of the constellation of geosynchronous spacecraft 89-046A, 90-095A, and 91-080B. The MPA consists of a single electrostatic analyzer (ESA) coupled to an array of channel electron multipliers, and it measures three-dimensional energy/charge distributions of both ions and electrons in a range of ~1 eV/q to >40 KeV/q. For use at this orbit, the instrument was designed for high sensitivity with moderate energy and angular resolutions. The ESA is composed of a set of spherical plates such that the bending angle from the center of the entrance aperture is a constant 60 degrees, independent of the polar angle of entry. Electrons and ions are analyzed alternately with this single ESA. After leaving the ESA, the particles are accelerated into an array of six spiral-configuration channel electron multipliers (CEMs). Each CEM covers a separate polar angle field of view (FOV). The FOVs are fan-shaped and centered at +/- 11.5, 34.5, and 57.5 degrees polar angle, where 90 degrees is the spin axis direction (actively controlled to point to the center of the earth). Three-dimensional measurements are obtained by using spacecraft rotation, at a nominal 6 rpm, to sweep the FOV through the full 360 degree range of spacecraft azimuth angle while recording counts in the six polar angle FOVs. Measurements are made in standard cycles at each of 24 angles (15 degree spacing) in azimuth during each 10 s spacecraft revolution. Approximately 92% of the unit sphere is observed by the MPA. Normal instrument operation is composed of five types of cycles arranged in an eight-cycle sequence that repeats every 86 s. This provides both two-dimensional and three-dimensional distributions, with varying resolutions. For more details of the instrument, see the paper by S. J. Bame et al., Rev. Sci. Instrum., 64, (4), pp. 1026-1033, 1993. The MPA KP data values are preliminary and have a number of problems which will be corrected when we revise our algorithms and re-process the data. However, that could be a while in coming. It is to be understood that the MPA data set contains very preliminary values (not publishable!) and any investigators interested in using them should contact us before embarking on any extensive study using them. Michelle Thomsen (S:ESSDP1::thomsen) The file format is NASA's Common Data Format (CDF, https://cdf.gsfc.nasa.gov). The data can be viewed using Autoplot (https://autoplot.org). The raw data in these files can be processed/understood via information contained in the Thomsen et al. tech report "Calculation of Moments from Measurements by the Los Alamos Magnetospheric Plasma Analyzer" (https://www.osti.gov/biblio/8188)