Polar (satellite)

Short description: NASA science spacecraft which studied the polar magnetosphere until 2008

Polar

Polar is the second of NASA's Global Geospace Science program

Names| GGS/Polar, ISTP/Polar, Polar Plasma Laboratory
Mission type| Earth observation
Operator| NASA
COSPAR ID| 1996-013A
SATCAT no.| 23802
Website| http://pwg.gsfc.nasa.gov/polar/
Mission duration| Planned: 2 years
Final: 12 years, 2 months, 3 days
Spacecraft properties
Manufacturer| Lockheed Martin Astro Space
Launch mass| 1,297 kg (2,859 lb)[1]
Dry mass| 1,028 kg (2,266 lb)[1]
Payload mass| 264 kg (582 lb)[1]
Dimensions| 2.4 × 1.8 m (7.9 × 5.9 ft)[1]
Power| 440 watts[1]
Start of mission
Launch date| February 24, 1996, 11:24 (1996-02-24UTC11:24) UTC[2]
Rocket| Delta II 7925-10 D233
Launch site| Vandenberg Air Force Base SLC-2W
End of mission
Disposal| Decommissioned
Deactivated| April 28, 2008 (2008-04-29)[3]
Orbital parameters
Reference system| Geocentric
Regime| Highly elliptical
Semi-major axis| 35,490.94 km (22,053.05 mi)
Eccentricity| 0.701992
Perigee altitude| 4,198.46 km (2,608.80 mi)
Apogee altitude| 54,027.15 km (33,570.91 mi)
Inclination| 78.63°
Period| 1,109.02 minutes
RAAN| 260.60°
Argument of perigee| 306.12°
Mean anomaly| 7.84°
Mean motion| 1.30°
Epoch| August 19, 2018, 04:42:45 UTC[4]
Revolution no.| 10,771
| Instruments

MFE| Magnetic Field Experiment
EFI| Electric Fields Instrument
PWI| Plasma Wave Instrument
HYDRA| Hot Plasma Analyzer Experiment
TIDE/PSI| Thermal Ion Dynamics Experiment/Plasma Source Investigation
TIMAS| Toroidal Imaging Mass-Angle Spectrograph
CAMMICE| Charge and Mass Magnetospheric Ion Composition Experiment
CEPPAD| Comprehensive Energetic-Particle Pitch Angle Distribution
UVI| Ultraviolet Imager
VIS| Visible Imaging System
PIXIE| Polar Ionospheric X-ray Imaging Experiment

International Solar-Terrestrial Physics Science Initiative

<- Wind

SOHO ->

The Global Geospace Science (GGS) Polar satellite was a NASA science spacecraft designed to study the polar magnetosphere and aurorae. It was launched into orbit in February 1996, and continued operations until the program was terminated in April 2008. The spacecraft remains in orbit, though it is now inactive. Polar is the sister ship to GGS Wind.

## Contents

* 1 Launch
* 2 Operations
* 3 Characteristics
* 4 Scientific instruments
* 5 Results
* 6 References
* 7 External links

## Launch

It was designed and manufactured by Lockheed Martin, and launched at 11:23:59.997 UTC on February 24, 1996, aboard a McDonnell Douglas Delta II 7925-10 rocket from launch pad 2W at Vandenberg Air Force Base in Lompoc, California , to study the polar magnetosphere.

The spacecraft was placed into a highly elliptical orbit with apogee at 9 Earth radii and perigee at 1.8 Earth radii (geocentric), 86 degrees inclination, with a period of around 18 hours. The apogee was initially over the northern polar region, but has since been precessing south at about 16° per year.

## Operations

Sensors on the spacecraft gathered multi-wavelength imaging of the aurora, and measured the entry of plasma into the polar magnetosphere and the geomagnetic tail, the flow of plasma to and from the ionosphere, and the deposition of particle energy in the ionosphere and upper atmosphere.

The nominal mission duration was two years, but was extended several times. Polar Mission Operations were finally terminated on April 28, 2008, after the spacecraft depleted its remaining fuel.[5][3]

## Characteristics

Polar is a cylindrical satellite of 2.4 meters in diameter and 1.8 meters in height built by the "Astro Space" division of Martin Marietta. WIND is a stabilized satellite rotation at a speed of 10 rpm about its axis which is maintained perpendicular to the plane of the ecliptic. A platform that serves as support for certain instruments (including imaging) require that their field of view is fixed is fixed to the top of the satellite and rotates in the opposite direction. Satellite walls are covered with solar cells that provide 440 watts of electricity including 186 W are used by the scientific instruments. The satellite has a mass of 1297 kg, including 269 kg of propellant and 264 kg payload. It is designed for a minimum lifetime of 2 years. Scientific data are stored on a digital recorder with a capacity of 1.3 gigabits and transmitted at a rate between 56 and 512 kb. Polar is the twin satellite of Wind.

## Scientific instruments

Polar carried 11 scientific instruments totaling a mass of 264 kg:

Five instruments studying the local electromagnetic fields at low frequency:

* MFE (Magnetic Field Experiment)
* EFI (Electric Fields Instrument)
* PWI (Plasma Wave Instrument)
* HYDRA (Hot Plasma Analyzer Experiment)
* TIDE/PSI (Thermal Ion Dynamics Experiment / Plasma Source Investigation)

Three instruments responsible for studying populations of particles associated with electromagnetic fields:

* TIMAS (Toroidal Imaging Mass Angle Spectrograph)
* CAMMICE (Charge and Mass Magnetospheric Ion Composition Experiment)
* CEPPAD (Comprehensive Energetic Particle-Pitch Angle Distribution)

Three imagers responsible for providing a comprehensive view of the processes that interact with the upper atmosphere:

* UVI (Ultraviolet Imager)
* VIS (Visible Imaging System)
* PIXIE (Polar Ionospheric X-ray Imaging Experiment)

## Results

Polar collected images of auroras in multiple wavelengths. She also measured the amount of plasma used in the polar regions of the magnetosphere, the flow of the latter in the ionosphere and the entry of other charged particles in it and in the upper atmosphere. For the first time the entire sequence of events initiated by magnetic substorms to the generation of the aurora was observed in detail. Analysis of the collected data determined that solar storms deposited such an amount of energy in the ionosphere that it stretched to fill the magnetosphere completely. Polar instruments were used during the primary mission of the THEMIS satellite between January and April for his study of magnetic tail.[1]

A time-lapse animation of aurorae over both Earth poles shows symmetries and simultaneous changes - the long-suspected aurora mirroring – in images from the Visible Imaging System (VIS).

This composite image contains the first picture of the Earth in X-rays, taken in March 1996 by Polar.

## References

1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 "Polar". eoPortal. European Space Agency. https://directory.eoportal.org/web/eoportal/satellite-missions/p/polar.
2. ↑ "Polar". NASA Space Science Data Coordinated Archive. NASA. March 21, 2017. https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1996-013A.
3. ↑ 3.0 3.1 Layton, Laura (April 28, 2008). "'Broken Heart' Image the Last for NASA's Long-Lived Polar Mission". NASA. https://www.nasa.gov/topics/earth/features/polar_heart.html.
4. ↑ "Polar - Orbit". Heavens-Above. August 19, 2018. https://heavens-above.com/orbit.aspx?satid=23802.
5. ↑ Nelson, Buddy (April 30, 2008). "Long-Lived NASA Polar Satellite, Built by Lockheed Martin, Ends Service After 12 Productive Years". Lockheed Martin. http://www.lockheedmartin.com/news/press_releases/2008/4-30-polarsat.html.

## External links

* Polar website at NASA.gov
* Old Polar website at NASA.gov

* v
* t
* e

Magnetospherics

Submagnetosphere|

* Atmospheric circulation
* Aurora
* Earth's magnetic field
* Geosphere
* Jet stream
* Polar wind

Earth's magnetosphere|

* Birkeland current
* Bow shock
* Ionosphere
* Magnetopause
* Magnetosheath
* Magnetosphere
* Magnetosphere chronology
* Magnetosphere particle motion
* Plasmasphere
* Ring current
* Van Allen radiation belt

Solar wind|

* Coronal cloud
* Coronal mass ejection
* Solar flare
* Geomagnetic storm
* Heliosphere
* Interplanetary magnetic field
* Heliospheric current sheet
* Heliopause
* Solar particle event
* Space climate
* Space weather

Satellites|

* Full list
* Arase (2016)
* Cluster II
* Double Star
* Geotail
* IMAGE
* MMS (2015)
* Polar
* THEMIS
* Van Allen Probes
* Wind

Research projects|

* EISCAT
* HAARP
* SHARE
* Unwin Radar
* SuperDARN
* Sura Ionospheric Heating Facility

Other magnetospheres|

* Hermian
* Lunar
* Jovian
* Ganymedian
* Saturnian
* Uranian
* Neptunian

Related topics|

* Flux tube
* Gas torus
* Lunar swirls
* Planetary rings
* Jupiter
* Saturn
* Uranus
* Neptune

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