Definitions

C/NOFS

C/NOFS

C/NOFS, or Communications/Navigation Outage Forecasting System is a satellite designed to investigate and forecast scintillations in the Earth's ionosphere. It was launched by an Orbital Sciences Corporation Pegasus-XL rocket at 17:01 GMT on 16 April 2008.

The satellite, which will be operated by the USAF STP, will allow the US military to predict the effects of ionospheric activity on signals from communication and navigation satellites, outages of which could potentially cause problems in battlefield situations.

C/NOFS has a three-axis stabalisation system, and is equipped with seven sensors. It was be placed into a low Earth orbit with orbital inclination of 13°, a perigee of 400 km and an apogee of 850 km. It carries the CINDI experiment for NASA. Launch was originally scheduled for 2003, but had been delayed due to a number of issues.

Scientific instruments onboard

The spacecraft payload consists of the following instruments:

  • Ion Velocity Meter (IVM): IVM consists of a pair of sensors designed to measure the in situ ion velocity vector, ion temperature, and ion composition. The IVM is provided by the William B. Hanson Center for Space Sciences at the University of Texas at Dallas. IVM is a component of the CINDI package funded by NASA.
  • Planar Langmuir Probe (PLP): A two sensor package consisting an ion trap designed to measure ion density fluctuations and a Langmuir probe. PLP is provided by the Air Force Research Laboratory.
  • Neutral Wind Meter (NWM): A two sensor package designed to measure the neutral wind velocity. NWM is provided by the William B. Hanson Center for Space Sciences at the University of Texas at Dallas. Like IVM, NWM is a component of the CINDI package funded by NASA.
    • Ram Wind Sensor (RWS): RWS measures the ram component of the neutral wind by ionizing a fraction of the incoming neutral gas then performing retarding potential analysis on those ions.
    • Cross Track Sensor (CTS): The cross track sensor is a hollow hemispherical dome divided into four independent chambers with a miniaturized Bayard-Alpert hot filament ionization gauge in each chamber. Four small holes in the dome allow the neutral gas to stream into the chambers. The pressure in any chamber will depend on the arrival angle of the neutral wind.
  • CORISS: The C/NOFS Occultation Receiver for Ionospheric Sensing and Specification (CORISS) instrument is a GPS dual-frequency receiver designed to measure line-of-sight TEC. CORISS is provided by the Aerospace corporation.
  • CERTO: the Coherent Electromagnetic Radio Tomography (CERTO) experiment is a radio beacon that will provide plasma density profiles and information on phase and amplitude scintillation of radio signals. CERTO is provided by the Naval Research Laboratory.
  • Vector Electric Field Instrument (VEFI): VEFI is a collection of instruments including 6 electric field booms, a 3-axis magnetometer, a spherical Langmuir probe, and a lightning detector. VEFI is provided by NASA Goddard.

Spacecraft design

Considerable effort went into making the vehicle a good platform for in situ ionospheric measurements. The solar arrays are body mounted to minimize their impact on the electric field measurements. The entire surface of the vehicle is electrically conductive and solar array contacts are covered in order to minimize spacecraft charging. Two star trackers are used to provide the pointing knowledge required by the experiments.

Current status

On 2008-05-28 the USAF Space Development and Test Wing announced its launch and early orbit portion of the spacecraft's operations had been completed successfully. On 2008-06-09 the manufacturer of the separation systems used to deploy the C/NOFS solar panels, payload antennas and magnetometer boom indicated they had all functioned correctly.

Publications

  • "A new satellite-borne neutral wind instrument for thermospheric diagnostics", Earle et al, Reviews of Scientific Instruments 78, 114051 (2007)
  • "C/NOFS: a mission to forecast scintillations", O. de La Beaujardiere, Journal of Atmospheric and Solar-Terrestrial Physics, 66 (2004) 1573-1591

References

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