ANDESITE is a Space-Based Wireless Sensor Network (SB-WSN) that addresses the limit of individual satellites’ ability to spatially and temporally resolve the information on various space phenomena. As a first mission, this small network of miniature CubeSats will attempt to resolve current densities at varying spatial resolutions in the near-Earth magnetosphere using measurements from Anisotropic Resistance Magnetometers. The data obtained from this mission will help map the current sheets of Region 1 and Region 2 Birkeland currents. It will also provide solid new constraints for models of auroral particle acceleration, wave particle interactions, ionospheric destabilization and other kinetic processes operating in the low-beta plasma of near Earth magnetosphere.
ANDESITE will rely on widely accessible space-grade hardware developed around the CubeSat concept. ANDESITE seeks to use this technology to design a set of interacting miniature Sensor Nodes, for high-resolution sensing of space and atmospheric environments. A 1U network manager called the Mule will integrate a Command and Data Handling Unit (C&DH) running Android OS to manage the constellation and data. Furthermore, the project focuses on developing hardware that is compatible with CubeSat deployment platforms. Our design allows a standard 3U P-POD to deliver a multi-node sensor network and the Mule.
The transport of energy between the magnetosphere and the outer atmosphere is mediated by magnetic field-aligned currents, or Birkeland currents. During extreme space weather, the Birkeland currents become highly structured, with a plethora of indirect evidence suggesting that the largest current densities are carried in filaments with cross-section approaching the electron gyro-radius [e.g., Chaston et al., 2007]. Although filamentation is a well-known feature of current carrying plasmas, the processes responsible for filamentation of the geospace plasma are poorly understood. The major obstacle to progress in this area is experimental; investigations of current filamentation require multi-point measurements from a dense network of magnetic sensors, coupled with a robust analysis strategy based in statistical inverse theory. The proposed ANDESITE architecture is ideally suited to fill this need.
The science objective of our initial ANDESITE deployment is to explore techniques by which we may progressively relax the geometric and time-stationarity assumptions as we increase the density and coverage of samples. Our exploration of the acquired data sets will include direct calculation of the components of curl-B, similar to the Enstrophy approach, in addition to exploration of basis expansion techniques, similar to AMPERE. The mission explores the trade- space of space, time, and resolution in a manner that complements prior efforts discussed above. The 10-nT sensitivity and 0.2 nT/ self-noise of the Honeywell magneto-resistive magnetometer [Magnes and Diaz-Michelena, 2009] lies between the capabilities of the Iridium magnetometers and the ST5 magnetometers. But, as was demonstrated through the AMPERE project, the signal covariance between sensor nodes can be exploited in the analysis to improve the reliability of the result.
The proposed 12-Sensor Node network represents a spatial sampling pattern that is also an interim between the AMPERE and ST5 experiments, but targeting small- to meso-scale variability in the current systems. In this regard, our mission constitutes an expanded, orbital, version of the Enstrophy rocket experiment.