Summary of the Frequency Agile Solar Radiotelescope (FASR) Project

Science Goals

The Frequency Agile Solar Radiotelescope is a multifrequency (0.05 - 21 GHz) imaging array composed of three sets of antennas (FASR-A: 45 antennas; FASR-B: 15 antennas; FASR-C: 15 dipole array elements). It is designed specifically for observing the Sun. It will produce high quality images with spatial resolution about 1" at 20 GHz, high spectral resolution (Dn/n ~ 1%) and high time resolution (20 ms for each band, 1 s for entire spectral range).

Based on extensive discussions among members of the scientific community, several areas have been identified in which FASR is expected to make significant new contributions:

• Nature and evolution of coronal magnetic fields
• Physics of solar flares
• Drivers of space weather
• The physics of the quiet Sun

In addition, the observational capabilities of FASR, which represent a quantum leap beyond current radio instrumentation, gives the instrument tremendous potential for new discoveries beyond any that we can now anticipate.

Unique Science to be Addressed

The spatially resolved microwave, decimetric, and meterwave spectrum allows FASR to bring to bear powerful, spectrally-based, radio diagnostics. The radio spectrum contains unique information about the solar atmosphere and the acceleration of energetic particles that cannot be studied in any other way. The unique science to be addressed includes:

• What is the nature of the coronal magnetic field?
• How does it evolve in time and space?
• How is magnetic energy stored?
• What is the physics of magnetic energy release?
• How are electrons accelerated?
• What are the relevant electron transport processes?
• How are coronal mass ejections initiated and accelerated?
• What is the origin of coronal shocks?
• How are solar energetic particles accelerated?
• What is the thermal structure of the solar atmosphere?
• How are the chromosphere and corona heated?
• How does the corona extend into the heliosphere?

FASR science is presented in more detail in the overview document and in a Kluwer Astrophysics and Space Science Library volume listed in the links at right.

Current Status

FASR was one of 17 projects recommended for this decade by the Astonomy and Astrophysics Survey Committee, and received the highest priority rating of the Solar and Space Physics Survey Committee in the "small projects" category. Some FASR subsystems underwent prototyping and testing during 2004-2007, such as the broadband feeds, the analog/digitial processing, and the 21 GHz optical link. An end-to-end design study resulted in the FASR reference instrument, which was the basis for costing and for creating the Operations and Maintenance Plan. The full construction proposal has just been submitted for FY 2009 funding. The five-year construction and commissioning puts completion of the project at 2013, although the first science results can be expected a year earlier..

Design Summary

The array will consist of three separate antenna systems in order to cover the entire 3 decades of frequency from 50 MHz to 21 GHz. The two highest bands will utilize 6 m and 2 m antennas, respectively. The low band will utilize fixed log-periodic dipoles, or similar feeds. The FASR specifications are shown in the table below.