SA13A-01
C/NOFS Early Results
The Communication/Navigation Outage Forecasting System (C/NOFS) satellite was launched on 16 April 2008 into a low inclination (13°), elliptical (400 x 850 km) orbit. The purpose of the C/NOFS Mission is to forecast ionospheric density and irregularities that adversely impact communication, navigation and surveillance systems. The satellite sensors measure the following parameters: ambient and fluctuating ion densities; ion and electron temperatures; neutral winds, AC and DC electric and magnetic fields. C/NOFS is also equipped with a GPS occultation receiver, and a radio beacon. Complementary ground-based measurements, as well as space weather models are an integral part of the Mission. In this talk, we will present results from the first campaigns and coordinated runs with other satellites.
SA13A-02 INVITED
Initial Observations from CINDI - C/NOFS : Views of the Ionosphere Under an Extremely Quiet Sun
The CINDI project is being conducted as part of the payload for the C/NOFS satellite. The present ionospheric and thermospheric measurements are associated with the lowest average monthly levels of F10.7 recorded since 1954. While these conditions represent observational challenges to the instrumentation, a remarkable picture of the ionosphere can be revealed by the orbit that scans all longitudes and local time, all altitudes between 400 km and 850 km and all latitudes between -12 and +12 degrees in about 60 days. During these very quiet solar conditions most of the neutral atmosphere is contracted to altitudes below the satellite perigee of 400 km with temperatures below 600 K. In the ionosphere the O+/H+ transition height falls to 450 km altitude during the nighttime and rarely rises above 800 km during the day. In this presentation we will describe the instrument performance capabilities to date and discuss the behavior of the ionosphere that is revealed by the initial few months of data.
SA13A-03 INVITED
Correlation of In-Situ Plasma Irregularities with Ground-Based Scintillation Measurements
The Planar Langmuir Probe (PLP) instrument on the C/NOFS satellite measures in-situ ion number density fluctuations at frequencies up to 1024 Hz. These measurements are used to construct phase screen representations of the effect of the ionosphere on trans-ionospheric radiowave propagation. Since its initialization in May, 2008, PLP has detected large numbers of highly structured ionospheric regions in the equatorial belt. We will present an overview of the measurements and will examine the relationships between the observation of in-situ irregularities and measurements of UHF and GPS scintillation from SCINDA sites beneath the satellite orbital track.
SA13A-04 INVITED
Initial Results from the Vector Electric Field Investigation on the C/NOFS Satellite
Initial results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. The DC electric field detector has revealed zonal and meridional electric fields that undergo a diurnal variation, typically displaying eastward and outward-directed fields during the day and westward and downward-directed fields at night. In general, the measured DC electric field amplitudes are in the 0.5-2 mV/m range, corresponding to E x B drifts of the order of 30-150 m/s. What is surprising is the high degree of large-scale (10's of km to > 500 km) structure in the DC electric field, particularly at night, regardless of whether well-defined spread-F plasma density depletions are present. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. On some occasions, localized regions of low frequency (< 8 Hz) magnetic field irregularities have been detected, suggestive of filamentary currents. Finally, the data set includes a wide range of ELF/VLF/HF waves corresponding to a variety of plasma waves, in particular banded ELF hiss, whistlers, and lower hybrid wave turbulence triggered by lightning-induced sferics. The VEFI data set represents a treasure trove of measurements that are germane to numerous fundamental aspects of the electrodynamics and plasma irregularities inherent to the Earth's low latitude ionosphere.
SA13A-05
CORISS Measurements of the Equatorial Ionosphere
The objective of the Communication/Navigation Outage Forecasting System (C/NOFS) is to develop the scientific understanding necessary to enable reliable predictions of ionospheric scintillation effects. The C/NOFS satellite incorporates a GPS occultation sensor known as CORISS, the C/NOFS Occultation Receiver for Ionospheric Sensing and Specification. The function of CORISS within the C/NOFS program is to provide measurements of ionospheric total electron content, electron density profiles (F- and E-region), and L-band scintillation for comparisons with ionospheric models used in the process of scintillation prediction. We present an overview the CORISS data during the initial months of the C/NOFS mission, with a focus on time periods associated with ground truth campaigns.
SA13A-06
Equatorial Irregularity Characterization with Scintillation and Total Electron Content Measurements from Space
Ionospheric measurements of TEC (Total Electron Content) and radio scintillations provide direct inputs for space-weather models and for tracking of ionospheric disturbances such as Spread-F. These measurements require propagation from a transmitter to a receiver through the F-region plasma. The C/NOFS (Communication/Navigations Outages Forecasting System) satellite, which is dedicated to the study of Spread-F was launched in April of 2008 in an elliptical (400 km x 850 km), 13 degree inclination orbit. C/NOFS carries a Naval Research Laboratory (NRL) three-frequency 150/400/1067 MHz CERTO (Coherent Electromagnetic Radio TOmography) beacon transmitter. In addition, the NRL CITRIS (Scintillation and TEC Receiver in Space) instrument is currently in orbit at 560 km altitude with 35 degree inclination on the STPSat1 satellite. The orbit periods of the two satellites are relatively close, so that the CERTO beacon stays in view of the CITRIS receiver for several days. In addition, the C/NOFS CERTO beacon and ground receivers can simultaneously measure TEC and scintillations on different paths. Similarly, when C/NOFS is not in view, CITRIS records TEC and scintillations from the global network of French DORIS beacons and from other satellites in low earth orbit (e.g. Taiwan ROCSAT3, DMSP/F15, RADCAL, GFO, etc.). Because of the approximately 95 min orbital periods, CITRIS will always make measurements at the same longitude as C/NOFS within 48 min. The ability to look at multiple paths is unique and useful for studying the spatial extent and time duration of Spread-F events. With the new CERTO and CITRIS satellite-to-satellite measurement capability it is possible to retrieve absolute TEC. During these measurement periods, the Langmuir probe data from PLP on C/NOFS can be cross-calibrated by using the TEC data. Another new capability for CITRIS is the ability to use three frequencies (150, 400, and 1067 MHz) for TEC measurements, which can be used to resolve 2Ĉ phase ambiguities. The first several months of joint measurements with the CERTO beacon on C/NOFS and the CITRIS receiver have provided unique and exciting data on geophysical plasma structures at low latitudes.
SA13A-07
Space-based Scintillation Nowcasting with the Communications/Navigation Outage Forecast System
The Air Force Research Laboratory¡¦s Communication/Navigation Outage Forecast System (C/NOFS) fuses ground- and space-based data in a near real-time physics-based model aimed at forecasting and nowcasting equatorial scintillations and their impacts on satellite communications and navigation. A key component of the system is the C/NOFS satellite that was launched into a low-inclination (13„a) elliptical orbit (400 km x 850 km) in April 2008. The satellite contains six sensors to measure space environment parameters including electron density and temperature, ion density and drift, electric and magnetic fields and neutral wind, as well as a tri-band radio beacon transmitting at 150 MHz, 400 MHz and 1067 MHz. Scintillation nowcasts are derived from measuring the one-dimensional in situ electron density fluctuations and subsequently modeling the propagation environment for satellite-to-ground radio links. The modeling process requires a number of simplifying assumptions regarding the three-dimensional structure of the ionosphere and the results are readily validated by comparisons with ground-based measurements of the satellite¡¦s tri-band beacon signals. In mid-September 2008 a campaign to perform detailed analyses of space-based scintillation nowcasts with numerous ground observations was conducted in the vicinity of Kwajalein Atoll, Marshall Islands. To maximize the collection of ground-truth data, the ALTAIR radar was employed to obtain detailed information on the spatial structure of the ionosphere during the campaign and to aid the improvement of space-based nowcasting algorithms. A comparison of these results will be presented; it appears that detailed information on the electron density structure is a limiting factor in modeling the scintillation environment from in situ observations.
SA13A-08
Optical Lightning Detection and and Vector Electric Field Measurements Gathered in the Low-Latitude Ionosphere by Probes on the C/NOFS Satellite
The Air Force Communication/Navigation Outage Forecast System (C/NOFS) satellite has, for the first time, successfully lofted both a DC-VLF vector electric field instrument and a pair of optical lightning sensors into the low latitude ionosphere in order to study these transients and their space weather effects. Because the C/NOFS orbit is near equatorial (+/- 13 degrees inclination), every single pass traverses dozens of lightning- producing storms, most notably in Africa, South America, and the South Pacific. This paper will describe lightning-induced electric field and optical transient measurements and provide an overview of the new results regarding lightning energy input into the ionosphere as well as their lightning-induced ionospheric irregularities. In addition, we couple the in situ measured electric field and optical waveforms with ground- based lightning location information provided by the World-Wide Lightning Location Network (WWLLN) in order to study the full propagation of the lightning electromagnetic pulse (EMP) from the source to the satellite location in the ionosphere.