Polar Mission Information

Mission Overview

Polar - Wind Graphic The Polar spacecraft was developed under the auspices of the Global Geospace Science (GGS) mission. Polar's purpose is to examine the polar regions of the Earth's magnetosphere. Launched on February 24, 1996, Polar entered a highly elliptical orbit with an apogee at 9 earth radii and perigee at 1.8 earth radii geocentric. The Polar spacecraft carries a myriad of instruments capable of studying energetic particles, magnetic and electric fields, and imaging auroral regions.

Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE)

The Polar Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE) consists of two sensor systems designed to measure the charge and mass composition within the earth's magnetosphere over the energy range of 6 keV/Q to 60 MeV/ion. The determination of the fluxes of various ion species and their abundances relative to other species will permit the CAMMICE team to investigate and identify mechanisms by which these charged particles are energized and transported from their parent source populations within Geospace. Professor Theodore A. Fritz of Boston University is the Principal Investigator of the CAMMICE investigation.

Instruments:

Heavy Ion Telescope:
The Heavy Ion Telescope (HIT) uses a three-element solid-state detector telescope to measure the rate of energy loss and the ion incident energy. These parameters permit a unique determination of the ion mass, elemental identification, and incident energy over the energy range from 100 keV per ion to 60 MeV per ion.
Magnetospheric Ion Composition Sensor:
The Magnetospheric Ion Composition Sensor (MICS) uses an ellipse-shaped electrostatic analyzer, a secondary-electron generation/detection system and a solid-state detector to measure the energy, time-of-flight, and the energy per charge of the incident ion flux. These three parameters permit a unique determination of the ion charge state, mass, and incident energy over the energy range from 6 keV/e to 400 keV/e.

Comprehensive Energetic Particle and Pitch Angle Distribution (CEPPAD)

The CEPPAD experiment consists of four sensors for investigating energetic particle phenomenon on the POLAR mission. These sensors provide 3-D proton and electron angular distributions in the energy range of ~20 keV to ~1 MeV, energetic proton and electron measurements extending to energies greater than ~10 MeV, high angular and time resolution in the source/loss-cone, and data on energetic neutral particles. All sensors operate in conjunction with special on-board data processing units which control sensor data acquisition modes while performing in-flight data processing, data compression, and telemetry formatting. Dr. J. B. Blake of the Aerospace Corporation in El Segundo, CA is the Principal Investigator of the CEPPAD investigation.

Instruments:

Imaging Electron Spectrometer (IES) and High Sensitivity Telescope (HIST):
The Imaging Electron Spectrometer (IES) uses ion-implanted silicon solid state strip detectors to sense energetic electrons. Simultaneous flux measurements as a function of pitch-angle and energy are achieved by the novel geometry of the IES sensor, which has a 180 x 35 degree field of view. The IES is sensitive to energetic electrons ranging from 30 keV to 500 keV. An aluminum mylar foil placed in front of each strip detector eliminates protons of energies below 350 keV as well as a light response.

The High Sensitivity Telescope (located under the IES) uses three detector elements to measure electrons from 350 keV to 10 Mev and protons from 2.15 to 80 Mev. Detector A is a 300 micrometer thick, 300 square mm surface-barrier. Detector B is a 2000 micrometer thick, 200 square mm ORTEC surface-barrier. Detector C is a Bicron plastic scintillator with a Hamamatsu R3668 photomultiplier tube. The HIST attempts to provide a "clean" measurement of very energetic electrons. A more detailed description of the operation of the HIST can be found here.
Imaging Proton Sensor (IPS):
The Imaging Proton Spectrometer (IPS) is similar in form and function to the IES. The IPS uses a monolithic ion-implanted solid-state detector that is discretely segmented into multiple pixels. The detector sits behind a collimation stack at the "focal plane" of a "pin-hole camera", thereby imaging a slice of phase space. Three identical heads, each with three non-overlapping look directions (20 deg x 12 deg) provide collectively an instantaneous snapshot of a 180 degrees x 12 degrees wedge of phase space. As a consequence of spacecraft rotation, the IPS maps out a full 4pi steradian image each spin period (~6 seconds). Flux measurements are obtained as a function of pitch-angle and energy each 1/32nd of a spin. A low energy threshold of ~12 keV is the result of an extremely thin detector "window" and low-noise support electronics. Sixteen energy bins span the low energy threshold to a maximum of ~1.5 MeV. Energy spectral resolution is programmable where both the low and high thresholds may be selected in-flight and where energy bins may be either linear or semi-logarithmic across that range. In-flight auto-calibration is achieved through an internal pulse generator consisting of both a discrete but calibrated dual-source and a semi-continuous uncalibrated source.