SSAEM Sensors Paul R Straus October 14, 2011

SSAEM KPPs, KSAs, and Programmatic Focus Ionospheric Scintillation: Communication/Navigation Outages Electron Density Profile: Ionospheric Specification/Forecasting KPPs directly drove SSAEM program’s focus on equatorial region Where ionospheric scintillation is most significant Where ionospheric densities are highest and have significant variability KSAs: Chosen to support “KPP areas” based on C/NOFS heritage In-Situ Plasma Fluctuations: indirectly helps specification of scintillating regions Electric Fields: driving forces relevant to both specification and forecast of scintillation/ionospheric structure (especially with Full Physics GAIM) In-Situ Plasma Temperatures: relevant to ionospheric models

SSAEM/COSMIC-2 Sensors & EDRs TriG GNSS Radio Occultation Sensor TEC, EDPs, L-Band scintillation RF Beacon 400/~960*/~2200* MHz beacon utilizing SCINDA ground sites Local TEC, UHF/L-band scintillation Velocity, Ion Density & Irregularities (VIDI) Sensor In-Situ Plasma Fluctuations, Electric Fields & Plasma Temperatures TriG will be on all COSMIC-2 satellites RF Beacon & VIDI will be on the low inclination COSMIC-2 satellites *Frequencies TBD

SSAEM Approach to Addressing Operational Scintillation/Ionospheric Specification Issues Measure it UHF/L-Band/S-Band: RF Beacon/Upgraded SCINDA L-Band: TriG Infer it In-Situ Plasma Fluctuations & Depletions: VIDI Models incorporating the deriving forces (PBMOD): VIDI Ionospheric Structures TriG & RF Beacon/SCINDA In-track Plasma Density: VIDI Models incorporating driving forces (e.g., Full Physics GAIM): VIDI Primary approach for KPP

VIDI Instrument Objectives & Approach Measure in-situ plasma parameters related to ionospheric specification and scintillation 3D plasma drifts (used to infer Electric Fields) Cross-track drifts to ±5 m/s accuracy In-track drifts to ±10 m/s accuracy Electron/ion density & composition (both to 5% accuracy) Electron/ion temperature (to 10% accuracy) Plasma density fluctuations (to 10% accuracy at 15 m horizontal resolution – 512 Hz sample rate) Approach: Gridded sensor apertures on the ram face of the spacecraft collect and analyze electron/ion (dependent on grid potentials) currents from the ambient plasma environment to enable determination of environmental parameters

VIDI/IVM Sensor Electronics and Aperture Plate

VIDI/SPLP Sensor Electronics and Aperture Plate

Density fluctuations observed by PLP VIDI In-Situ Sensor Observe/characterize in-situ structures associated with scintillation Horizontal measurement of density fluctuations can be used to estimate S4 scintillation parameter Observations of plasma drifts (Electric Fields) can be used to drive ionospheric models SatCom/GPS Satellite Density fluctuations observed by PLP Irregularities in Ionosphere A Planar Langmuir Probe (PLP) will directly address the two KPPs of scintillation and Electron Density Profiles (EDPs) in a simple affordable manner. Scintillation: Scintillation is caused by chaotic fluctuations in the index of refraction along a path between a satellite and a ground receiver produced by turbulent plasma. It is not practical to directly measure the plasma density along a vertical path, but it is easy to measure the plasma density along a horizontal satellite track. The horizontal density structures observed by PLP can be translated into a vertical distribution of density fluctuations and used to calculate the level of scintillation that an observer on the ground would see. This measurement would provide global equatorial coverage of the presence of scintillation ever 90 minutes. EDPs: PLP does not directly measure vertical electron density profiles but provides a point of truth that can be used to guarantee that model outputs of the ionosphere are correct. Scintillation, comm dropouts, GPS loss of lock In-Situ observation Climo Receiver Model w/ E-field

RF Beacon Instrument Objectives & Approach Enable measurement of equatorial scintillation (in concert with a network of ground receivers) throughout the UHF/L-band frequency range Separate UHF & L-band frequencies required S-band frequency to provide stable reference for phase scintillation measurements under strong scintillation conditions S4 & σφ measurements required to 0.1 & 0.1 radians uncertainty, respectively Enable measurement of slant-path TEC using ground receivers Measurement Accuracy of 0.01 TECu for relative TEC (threshold) Measurement Accuracy of 3 TECu for absolute TEC (objective)

RF Beacon Ground-based measurements of scintillation using SSAEM Beacon signals will enhance probability of scintillation detection and improve temporal and spatial resolution relative to current SCINDA products Beacon TEC measurements provide ancillary data for GAIM Beacon Data SCINDA RADAR MAP 2+ hour forecast for scintillation downstream Current Product Improved Product A satellite beacon/receiver pair provides an observation of what is below the satellite. However it requires ground assets (either ground-based receivers or transmitters). This was a single example of how addition structures were detected when a beacon passed over a SCINDA site. SCINDA SPECIFICATION MAP Single look direction to GEO satellite Increased spatial coverage with beacon Current Product With Beacon

Coverage/Refresh Analysis for Scintillation Specification/Prediction Analysis performed to assess performance of COSMIC-2 (equatorial component) relative to single free flyer & scintillation development time scales Mapping of irregularity regions along geomagnetic field lines results in excellent performance

Scintillation Coverage vs. Refresh COSMIC-2 Free-Flyer RF Beacon SCINDA Ground Stations COSMIC-2 30N 30S Existing Sites UN IHY Sites Other/collaboration COSMIC-2 Scintillation Evolution Time Scale: 15-30 minutes Free-Flyer TriG COSMIC-2 SSAEM Will Completely Characterize the Equatorial Scintillation Environment Free-Flyer VIDI (Fluctuations)

CORISS/ALTAIR Geometry 21 Apr 2009 10:09 UT Tangent Point Track C/NOFS Orbital Track Apex Altitude 300-400 km 13

Coherent Returns from ALTAIR & CORISS SNR CORISS occultation tangent points CORISS SNR Bottomside Max Height ALTAIR indicates location of small-scale (40cm) irregularities relative to the CORISS tangent point track. CORISS detects ionospheric irregularities only within F region, while high sensitivity of ALTAIR reveals structure at slightly lower altitudes. Mean scattering location is slightly westward of the CORISS tangent point track. 10

CORISS Observations & Simulation Assume weak scattering: PRN 16 Given propagation orthogonal to B, then where d is C/NOFS-GPS distance Yields ds ~ 630 km (t.p. is ~500 km) Determine irregularity strength, region size, spectral slope, & BG density profile from ALTAIR, SCINDA & CORISS measurements Fresnel null frequencies Multiple Phase Screen Simulation CORISS Break frequency 15

Multiple Phase Screen Simulation of CORISS Data MPS Simulation CORISS 15

Coverage/Refresh Analysis for Ionospheric Specification/Prediction Analysis assumptions: Evaluation of ability to “populate” a GAIM-like model 1°×2.5°×20-50 km voxel granularity In-situ density observations provide exact specification of voxel density TriG TEC observations provide data for tomographic-like reconstruction Require two observations through a voxel to be considered fully specified Analysis region: ±30° geomagnetic latitude range over 100-800 km altitude range, bounded by 300 km field lines at ±30°

Ionospheric Specification Coverage vs. Refresh COSMIC-2 will cover 50% of the equatorial region every hour Only includes equatorial component of COSMIC-2 constellation: actual performance will be better If Electric Fields can be utilized in operational model, performance may improve due to leveraging of physics of magnetic field mapping COSMIC-2 Free-Flyer TriG+VIDI (In-Situ Density) Bulk Ionosphere Evolution Time Scale: ~60 minutes COSMIC-2 SSAEM Will Measure Both the Background Ionosphere and the Most Significant Driving Force Relevant to Low Latitude Ionospheric Modeling Free-Flyer VIDI (E-Fields)