Solar Imaging Radio Array (SIRA) R. MacDowall, N. Gopalswamy, M. L. Kaiser, M. J. Reiner Code 695 NASA Goddard Space Flight Center Greenbelt, MD USA sira.gsfc.nasa.gov

Overarching science question: what is the evolution of CME- driven shocks & CMEs from the Sun to 1 AU, and what are the resulting magnetospheric responses? CME structure, propagation, & evolution, including topologies of interacting CMEs Evolution of intermediate-scale solar wind structure and its effect on CMEs Structure and dynamics of energetic electron beams from CME shocks & flares Space weather prediction using radio imaging, including an exterior view of the meso-scale magnetospheric response to space weather Mapping “astrophysical” sources, including coherent sources, steep-spectrum “fossil” radio galaxies, & serendipitous discoveries

3 Solar Radio Bursts – corona to 1 AU Note that radio imaging is complementary to coronagraphs, all-sky imagers, and scintillation observations. ?

4 Measurement improvement over state of the art: SIRA will provide the first high resolution imaging in the 0.1 to 10 MHz window SIRA array scattering

5 Roadmaps, history, schedule Science Roadmaps: Understand the structure and dynamics of … the solar wind; understand the response of magnetospheres; predict … the evolution of solar disturbances as they propagate in the heliosphere and affect Earth (SEC Roadmap RFA’s 2003) Previous MIDEX proposals (Astronomical Low Freq Array) –ALFA 1 (1995) – primarily astrophysics (JPL) –ALFA 2 (1998) – sub’d to both Astrophysics & Sun-Earth (JPL) –SIRA (2005) – first submission of Sun-Earth proposal by GSFC Schedule: Jan 2005 – Blue team Science review April 2005 – Blue team Science Implementation review Sep Mission design/implementation complete Focus on simplicity, reliability, and cost credibility

6  12 – 16 microsats required for adequate # of baselines (microsat concept at right from OSC proposal; similar to GSFC IMDC design)  Lunar flyby provides rapid insertion into “retrograde” orbit at ~500,000 km (~80 RE) from Earth  Spring forced deployment provides initial Δv to put microsats on 10 km sphere  X-band direct-to-ground downlink from μsats  Science data centers at MIT and GSFC  “Pathfinder” for microsat constellations Overview of SIRA mission design  Orbital Sciences (OSC) recently selected as spacecraft provider with Partnership Opportunity Document (POD)

7 SIRA technology issues What are the top technical challenges? –deploying and operating a ~16 microsat cluster (note: OSC Orbcomm & ROCSAT heritage; THEMIS is a 5 s/c mission “breaking the ice”) –full-sky aperture synthesis imaging (note: ongoing work for wide-field ground-based arrays – Long Wavelength Array (LWA), etc.) Is new technology needed? –Technology is at high TRL levels –Radio receivers: TRL 6 –Radio dipoles:TRL 9 –Carrier deployment mechanism: TRL 9 –Carrier flight software/components: TRL 5 –Cluster ops software/procedures: TRL 5 –Intersatellite ranging (3 m resolution): TRL 5, increasing to 6 by 2005, due to ST 9 & MMS LWA

8 SIRA heritage / partnerships SIRA science partners (and contributions): Jet Propulsion Laboratory – aperture synthesis imaging Mass. Institute of Technology – science data center UC Berkeley – dipole antennas, solar wind, EPO Catholic University – solar & IP radio astronomy University of Iowa – planetary radio astronomy Lockheed Martin – coronal radio astronomy, processing Nat’l Radio Astronomy Obs. – IP medium, corona Naval Research Laboratory – imaging; astrophysics Observatoire de Paris-Meudon – radio receivers Uppsala University – radio receivers, miniaturization Swinburne University – aperture synthesis imaging GSFC science team and partners bring strong heritage to space-based radio astronomy (ISEE-3, Voyager, Galileo, Ulysses, Wind, STEREO) With OSC as a partner, we have all needed components for a low-frequency, space-based radio interferometry mission GSFC internal partnerships: systems engineering proposal & project management flight dynamics ranging & other consultations SIRA microsat deployment

9 Summary a mission central to NASA Sun Earth Connections and LWS goals & objectives, with important applications to the Exploration Initiative (space weather prediction) the first high resolution imager of solar radio emissions at < 15 MHz ( AU) built on GSFC, JPL, NRL, MIT, and UCBerkeley’s considerable expertise in solar, heliospheric, planetary, and astrophysical space- based radio astronomy; radio imaging is the logical next step an ideal entry position for a significant microsatellite constellation (12-16 microsats) with simple spacecraft and instruments in a moderate radiation environment a significant opportunity to conduct interferometry from space with applications to many future missions SIRA is: