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Two missions presently under development by the United States Air Force Academy (USAFA), FalconSAT-2 and FalconSAT-3, include mission scientific objectives targeting the study of ionospheric F region plasma density depletions and topside bubbles associated with the so-called Equatorial Spread F (ESF) phenomena. The Miniature Electrostatic Analyzer (MESA), a USAFA-designed patch sensor that measures differential energy fluxes of electrons from 0.05 to 13 eV in six channels, is the primary experiment aboard FalconSAT-2, a 25-kg microsatellite intended for launch into an International Space Station (ISS) orbit via the Space Shuttle. Because the orbit will be approximately 360 km in altitude and of 52° inclination, FalconSAT-2 observations will complement those of low latitude missions (e.g., C/NOFS) and polar latitude, higher altitude missions (e.g., DMSP). Realistic internal magnetic field models demonstrate that field lines with apex heights of 1500 km (representing the upper altitude limit of equatorial plasma bubbles) may intersect the orbit plane at dip latitudes greater than 35°. Thus, FalconSAT-2 will be able to observe plasma depletions that have propagated poleward along the field lines and lower in altitude, depletions that may not be observed with the high altitude DMSP and the low latitude C/NOFS. Additionally, there may be opportunities for FalconSAT-2 to make simultaneous multipoint in situ measurements of large-scale plasma bubbles with other low altitude satellites, such as C/NOFS and DMSP. We will present a statistical analysis of the probability of making such measurements using nominal orbital parameters of the relevant spacecraft. Finally, a description of the FalconSAT-3 follow-on mission, including scientific objectives associated with seeking kinetic effects, is presented.

A satellite mission to investigate ionospheric equatorial spread-F phenomena is presently under development by faculty and cadets at the United States Air Force Academy (USAFA). FalconSat-2 is a low altitude (350 km) medium inclination (52 degrees) microsatellite whose scientific mission is to measure in situ plasma density along the satellite's orbital track to detect plasma depletions with spatial sizes of 2-10 km and depletion depths up to three orders of magnitude. Plasma depletions of this size and depth are notorious for their deleterious effects on radio communications, and their presence is common in the night-time F region ionosphere. Since it is desired to detect plasma depletions with sharp boundaries (i.e., a reduction in plasma density by a factor of 1000 over 2 km in space), and to account for diurnal variations in the ambient ionosphere, it was necessary to target the capability of making plasma density measurements that covered a dynamic range of 5 orders of magnitude and a sampling rate of 10 measurements per second. To meet these demanding measurement requirements, a novel electrostatic analyzer has been designed by USAFA faculty. The Miniature Electrostatic Analyzer (MESA) is a patch sensor consisting of a stack of insulated, lithographically patterned steel plates that form an array of electrostatic lenses.