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COMMUNICATION/NAVIGATION OUTAGE FORECASTING SYSTEM

Posted 7/21/2008 Printable Fact Sheet

The Communication/Navigation Outage Forecasting System satellite was launched April 16, 2008. The C/NOFS mission is a prototype of an operational system to forecast the ambient ionosphere and scintillations.

Scintillations are caused by naturally occurring irregularities and lead to fluctuations in communication signals that decrease satellite-to-ground throughput and delay signal acquisition. C/NOFS will alert users of impending UHF and L-band satellite communication outages, GPS navigation degradations, and radar tracking errors.

The goal of the C/NOFS mission is to detect regions of active scintillation, forecast areas of scintillation three to six hours before onset and improve estimates of scintillation probability up to 120 hours in advance.

C/NOFS includes three core elements: a satellite carrying several ionospheric sensors, complementary ground-based instruments located around the world, and models and user products to provide tailored outage forecast maps.

C/NOFS is a joint project of the DOD Space Test Program and the Air Force Research Laboratory's Space Vehicles Directorate. Project participants include the National Aeronautics and Space Administration, the University of Texas at Dallas, the Naval Research Laboratory and the Aerospace Corp.

The C/NOFS satellite is flying in a low inclination (13 degrees) elliptical (401 x 867 km. altitude) orbit.

The six onboard instrument packages are the Planar Langmuir Probe; Vector Electric Field Instrument; Neutral Wind Meter; Ion Velocity Meter; C/NOFS Occultation Receiver for Ionospheric Sensing and Specification, a GPS dual-frequency receiver for remote ionospheric sensing; and Coherent Electromagnetic Radio Tomography, a coherent radio beacon.

Mission 

The C/NOFS satellite mission has two phases, survey mode and forecast mode. During survey mode the C/NOFS sensors will collect as much data as possible to identify the key parameters for predicting scintillations. Survey mode data will be used to validate models and forecasting tools developed prior to launch. C/NOFS will operate in survey mode for the first few months of the mission, then transition to forecast mode for the remainder of the payload operations. All data will be collected throughout the mission via downlink to tracking stations. In addition, data will be sent back in real time with the aid of the NASA Tracking and Data Relay Satellite System geosynchronous relay satellites.

Instruments 

C/NOFS is the first satellite solely dedicated to forecasting ionospheric irregularities and radio wave scintillations. The sensor suite on C/NOFS is richer than that of any previously flown low-altitude equatorial satellite. A broad range of ground-based measurements will complement the space data. In addition, data from several other satellites and rocket experiments will augment the C/NOFS observations. Several campaigns are planned to validate operational forecasts, acquire data to achieve the science goals, and test the theoretical models.

C/NOFS Spacecraft Instrumentation

Name Measured Parameters  Organization 
PLP 
Planar Langmuir Probe
Electron density 
Electron temperature 
Power spectral densities
AFRL
VEFI 
Vector Electric Field Instrument
Vector DC & AC electric fields
Magnetic fields
Relative plasma density
Optical lighting emission
NASA Goddard Space Flight Center
IVM
Ion Velocity Meter
Vector ion drift velocities
Ion temp
Ion composition
University of Texas, Dallas
NWM
Neutral Wind Meter
Vector neutral wind velocities University of Texas, Dallas
CORISS
C/NOFS Occultation Receiver 
for Ionospheric Sensing and Specification
Ne profiles 
Line-of-sight TEC 
Space-to-space scintillation 
Stratospheric refractivity
The Aerospace Corp.
CERTO
Coherent Electromagnetic Radio Tomography
Space-to-ground scintillations
Ne reconstruction
Naval Research Laboratory

The principal element of the ground segment of C/NOFS is the Scintillation Network Decision Aid, a system of ground-based receivers which monitor the radio link to spacecraft in geosynchronous orbit. The stations are all located within 20 degrees of the Earth's magnetic equator.

Data from the satellite instruments and the SCINDA sensors will be made available to science investigators. Information about these data is provided in each instrument Web page.

Scientific efforts planned to validate the first generation of scintillation forecasting products and facilitate product improvements are described in the C/NOFS Science Plan (Technical Report AFRL/VS - TR-2003-1501, PDF file, 3.5 Mb). Part 1, Part 2

There are many technical challenges to be addressed as part of the C/NOFS project. These are described in an article entitled "C/NOFS: a Mission to Forecast Scintillations" (PDF document, 660 kb) which was published in the Journal of Atmospheric and Solar-Terrestrial Physics

The main science questions are: 

Ambient ionosphere Accurately specify ambient ionosphere from C/NOFS data
Forecast several hours ahead ambient ionosphere and ascertain how prediction accuracy decreases with prediction interval
Electric fields Separate and predict various electric field sources
Forecast strength of pre-reversal enhancement
Growth rate approximation Infer linear growth rate parameters along a flux tube to predict onset of R-T instability
Explain scintillation day-to-day variability
Non-linear development of plasma irregularities Determine irregularity strength as a function of time and space
Model and observe evolution of equatorial plasma bubbles and irregularity spectra
Plasma turbulence spectrum  Determine direction and wavelength of electrostatic plasma waves
Characterize plasma turbulence along depletion walls
Scintillation Determine relative influence of Bragg and Fresnel scattering
Infer phase and amplitude scintillation from in situ density fluctuations
Scintillation climatology Improve scintillation climatology model and understand physical mechanisms responsible for observed variations with space, season, activity indices, etc
Determine persistence statistics to improve long term outlook (3-day prediction)

The last meeting of the C/NOFS Science Team took place in Estes Park, Colo., in January 2005. The next science team meeting is planned for early 2009. For information on future meetings contact Dr. O. de La Beaujardiere at 781-377-2760. 

(Current as of July 2008)


For more information contact:

377th Air Base Wing Public Affairs
1000 Wyoming Boulevard SE, Suite 1A
Kirtland AFB, NM 87117-5776
DSN 246-5991, Commercial 505-846-5991





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