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Polar

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Polar Credit: Manufacturer Image

Status: Operational 1996. First Launch: 1996-02-24. Last Launch: 1996-02-24. Number: 1 . Gross mass: 1,300 kg (2,800 lb). Height: 1.85 m (6.06 ft).

Polar, and its sister spacecraft Wind, were NASA's contribution to the International Solar Terrestrial Program (ISTP), an international effort to quantify the effects of solar energy on the Earth's magnetic field. The Polar mission's specific objectives were to (1) investigate energy input to the ionospheric region through the day side cusp; (2) determine the mechanisms of ionospheric plasma outflow; (3) study the characteristics of the auroral plasma acceleration regions; (4) provide global, multispectral auroral images of the footprint of magnetospheric energy disposition into the ionosphere and upper atmosphere; (5) help determine the role of the ionosphere in sun storm phenomena and the overall magnetospheric energy balance; and (6) document ions leaving the atmosphere and subsequently appearing in the solar wind, or electrons of solar wind origin precipitating to auroral altitudes.

Data from Polar would be correlated with data from ground-based scientific observatories and the other spacecraft in the ISTP program (Wind, Geotail and SOHO (the Cluster spacecraft would also have participated, but were destroyed during launch)) to better understand the physical effects of solar activity on interplanetary space and the Earth's space environment.

The spacecraft was cylindrical with body mounted solar arrays, and spin stabilized at 10 rpm. Two pairs of wire booms for the Plasma Wave Instrument (PWI) experiment protruded from the body, as well as one belt antenna and four low-gain antennas.

The payload included:

• Plasma Wave Investigation (PWI) - designed to provide comprehensive measurements of plasma wave phenomena in the high latitude auroral zones, day side magnetic cusp regions, plasmasphere and plasma sheet.
• Fast Plasma Analyzer (HYDRA) - measured the rapid very low energy of the 3-dimensional ion and electron distribution function.
• Magnetic Fields Experiment - a magnetometer designed to measure the magnetic fields in the high and low altitude polar magnetosphere. This experiment would investigate the behavior of field-aligned current systems and the role they play in the acceleration of particles and the dynamics of the fields in the polar cusp, magnetosphere, and magneto-sheath.
• Toroidal Imaging Mass-Angle Spectrograph (TIMAS) - measured the 3-dimensional velocity distribution functions of all major magnetospheric ion species.
• Electric Field Instrument (EFI) - measured the three components of the ambient vector electric field and the thermal electron density.
• Thermal Ion Dynamics Experiment (TIDE) and Plasma Source Instrument (PSI) - would track the outflow of ionospheric plasma throughout the magnetosphere.
• Ultraviolet Imager (UVI) - a two dimensional imager sensitive to far ultraviolet wavelengths with an 8 deg. circular FOV. The instrument would conduct observations of both the sunlit and nightside polar regions in the far ultraviolet wavelengths to help quantify the overall effects of solar energy input to the earth's polar regions.
• Visible Imaging System (VIS) - a set of three low-light-level cameras designed to provide images of the aurora.
• Polar Ionospheric X-ray Imaging Experiment (PIXIE) - would measure the spatial distribution and temporal variation of x-ray emissions in the energy range 3 to 60 keV from the earth's atmosphere.
• Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE) - would determine the composition of the energetic particle populations of the Earth's magnetosphere to identify how these charged particles were energized and transported from their source to the magnetosphere.
• Comprehensive Energetic Particle Pitch Angle Distribution

• Polar - . Mass: 1,300 kg (2,800 lb). Nation: USA. Agency: NASA Greenbelt. Class: Earth. Type: Magnetosphere satellite. Spacecraft: Polar. USAF Sat Cat: 23802 . COSPAR: 1996-013A. Apogee: 50,423 km (31,331 mi). Perigee: 5,554 km (3,451 mi). Inclination: 86.30 deg. Period: 1,070.20 min. HEO. Fields and particles, auroral studies; part of International Solar Terrestrial Physics program..