The second Radio Aurora Explorer (RAX‐2) satellite has completed more than 30 conjunction experiments with the Advanced Modular Incoherent Scatter Radar chain of incoherent scatter radars in Alaska and Resolute Bay, Canada. Coherent radar echoing occurred during four of the passes: three when E region electron drifts exceeded the ion acoustic speed threshold and one during HF heating of the ionosphere by the High Frequency Active Auroral Research Program heater. In this paper, we present the results for the first three passes associated with backscatter from natural irregularities. We analyze, in detail, the largest drift case because the plasma turbulence was the most intense and because the corresponding ground‐to‐space bistatic scattering geometry was the most favorable for magnetic aspect sensitivity analysis. A set of data analysis procedures including interference removal, autocorrelation analysis, and the application of a radar beam deconvolution algorithm mapped the distribution of E region backscatter with 3 km resolution in altitude and ∼0.1° in magnetic aspect angle. To our knowledge, these are the highest resolution altitude‐resolved magnetic aspect sensitivity measurements made at UHF frequencies in the auroral region. In this paper, we show that despite the large electron drift speed of ∼1500 m/s, the magnetic aspect sensitivity of submeter scale irregularities is much higher than previously reported. The root‐mean‐square of the aspect angle distribution varied monotonically between 0.5° and 0.1° for the altitude range 100–110 km. Findings from this single but compelling event suggest that submeter scale waves propagating at larger angles from the main E×B flow direction (secondary waves) have parallel electric fields that are too small to contribute to E region electron heating. It is possible that anomalous electron heating in the auroral electrojet can be explained by (a) the dynamics of those submeter scale waves propagating in the E×B direction (primary waves) or (b) the dynamics of longer wavelengths.

The Radio Aurora Explorer CubeSat detected the first radar echoes during the solar storm of March 8, 2012. The 300 s ground‐to‐space bi‐static radar experiment was conducted in conjunction with the Poker Flat Incoherent Scatter Radar in the local morning (∼8 am) over Poker Flat, Alaska. The geomagnetic conditions for theEregion field‐aligned irregularity generation were optimal due to strong (about 1500 m/s)F region ion drifts and sufficient E region ionization (electron densities were ∼2 × 1011 m−3). The corresponding Eregion electric field of ∼80 mV/m was larger than the excitation threshold for the Farley‐Buneman instability. An auto‐correlation analysis resolved, for the first time, the distribution of auroralEregion backscatter with 3 km resolution in altitude and sub‐degree resolution in aspect angle. Moreover, the measured Doppler velocities of the UHF scatter shows the phase speed saturation of the meter‐scale plasma waves. The measured Doppler velocity is in excellent agreement with theCs cos θ formula for auroral E region irregularities.

The goals of the Climate Monitoring CubeSat Mission (CM2) are to accelerate climate projection by obtaining global temperature, tidal and wave measurements with a simple CubeSat-based imaging spectrograph; and to demonstrate how a high-resolution imaging spectrograph can be deployed on a CubeSat satellite. In the middle atmosphere (50 - 100 km), beyond the reach of balloons or satellites, thermal signatures of CO2 radiation and wave activity have been largely missing from climate model inputs. This paper outlines an instrument to advance the state of the art in atmospheric climate projection by providing critical global measurements of middle-atmosphere temperatures and waves with a CubeSatscale imaging spectrograph. The CM2 will remotely sense middle-atmosphere temperatures and waves at ~90 km by analyzing spectra of intrinsically bright molecular oxygen emissions at near-infrared wavelengths in the O2 atmospheric band. The core instrument will be a miniaturized imaging spectrograph based on a monolithic spatial heterodyne spectrometer (SHS). This spectrograph will have sensitivity and spectral resolution to extract temperatures with 10° K precision and waves with 4 km scale resolution along a ~200 km cross-track swath. The SHS is significantly more robust than conventional interferometers, and thus better suited to space-based observation. Acquiring high-resolution middle-atmosphere temperature, tidal, and wave data on a daily, global basis will significantly improve climate models, and will help assess long-term greenhouse gas mitigation policy impact on upper-atmosphere thermal signatures. The CM2 program will also establish the efficacy of highresolution CubeSat-based broadband (near-IR to UV) spectroscopy for application to other atmospheric research missions.

Tail fast flows have been associated both with the onset of substorms and with auroral Poleward Boundary Intensifications (PBIs) that extend equatorward as streamers. We study here a series of bursts of fast tail flow that occurred on 5 March 2008 when four of the THEMIS probes were aligned in the tail from mid-tail to inner magnetosphere and were in good conjunction with the Sondrestrom Incoherent Scatter Radar. The series of burst are identified as two separate events. We find that the first event is associated with a small substorm onset, and the second with a PBI and then possibly another onset. The ionospheric flow signatures of the substorm and the PBI are distinctly different: the substorm onset is characterized by flow enhancement in the polar cap several minutes before onset and by sudden ionospheric flow reduction at onset, while the PBI is accompanied by a flow enhancement directed primarily equatorward and intruding from the polar cap into the plasma sheet. Citation: Zesta, E., et al. (2011), Ionospheric convection signatures of tail fast flows during substorms and Poleward Boundary Intensifications (PBI), Geophys. Res. Lett., 38, L08105, doi: 10.1029/2011GL046758.

In the summer of 2007, a noctilucent cloud (NLC) campaign was organized in Alaska. Radar, lidar, and photographic methods were used. Due to lighting conditions, the campaign was carried out near the end of the NLC season. Sporadic radar and lidar echoes were obtained until the very end of the campaign, when an exceptionally intense event occurred on the local time night of 10–11 August. This late‐season event followed the launch of the space shuttle on 8 August. At least twice before, solstice launches of the shuttle have been followed by unique observations of NLC and sporadic iron layers in the polar regions. This was the case here as well. The iron layer increased in altitude and density, the latter by a factor of 20, compared to the previous night. And, for the first time, (1) polar mesospheric summer echoes (PMSE) were recorded by a radar in an event of this nature and (2) an intense sporadic E layer was collocated with the iron atom layer. At the UHF radar frequency used, very large Schmidt numbers are required for PMSE. Indeed, the PMSE was found at and just above the particles responsible for Mie scatter. Such large particles are likely needed to yield large Schmidt numbers. Additionally, similar lidar and sporadic E layers were detected over Greenland on the previous night. Here we consider the ion chemistry that could lead to the collocated atom and iron layers and conclude that considerably enhanced water vapor content was required.

The major design driver for the Dipping Thermospheric Explorer (DipTE) CubeSat mission is that the satellite shall fly a significant amount of orbit arcs at altitudes of 300km and below. It is assumed that the DipTE satellite will be released in a circular orbit above the altitudes of scientific interest for the mission. A propulsion system will be employed to make the orbit elliptic and satisfy the design driver The apogee of the elliptic orbit will be at the altitude of the initial circular orbit. The inclination of the orbit will stay the same. A few design iterations of the mission converged to a satellite configuration capable of storing 0.375 kg of propellant, and a propulsion system with a specific impulse I(sp) of 86 s. About 90 % of the total impulse of 313 Ns stored on board was budgeted to perform orbital maneuvers, with a 1 N thruster orbital maneuvering thruster (OMT).The remainder of 10 % of the propellant mass has been budgeted for attitude control maneuvers, such as those performed during detumbling and initial attitude acquisition. The attitude control maneuvers are performed with the thrusters of a reaction control system (RCS). The 12 two-dimensional (2D) microthrusters of the RCS produce 40 mN each and are installed such that they provide three-axis control of the spacecraft.This paper describes the preliminary design of the propulsions system.

EXECUTIVE SUMMARY We describe a nadir-viewing far-ultraviolet (FUV) photometer concept as a complementary sensor to GPS radio occultation (GPSRO) techniques to meet space weather monitoring objectives for total electron content (TEC). The Evolved Tiny Ionospheric Photometer (ETIP) addresses the need for compact spaceflight sensors that contribute to ionospheric density profile specification and data assimilation. Photometric measurements of oxygen nightglow at 135.6 nm are operationally equivalent to TEC measurements for the purpose of ionospheric specification and forecasting. FUV nadir photometry is a powerful technique to accurately measure ionospheric structures in the presence of large gradients—a problematic measurement scenario for GPSRO methods. The ETIP sensor design enhances reliability, performance, lifetime, and manufacturability of the flight-proven Tiny Ionospheric Photometer (TIP) sensor, in operation for over four years on the COSMIC mission. We incorporate innovative design elements from a new low size, weight, and power ionospheric photometer, developed by SRI International (SRI) for NRL’s Space Weather CubeSat mission, to achieve an evolved design which provides improved duty cycle, signal-to-noise, sensitivity, and redundancy. The ETIP measures the naturally-occurring 135.6 nm radiant emission produced by electron-ion recombination processes to characterize horizontal ionospheric gradients that can compromise GPS occultation retrievals, to identify the presence of ionospheric depletions, and to improve the fidelity of global ionospheric specification. ETIP collects ionospheric measurements on the nightside (where horizontal gradients are strongest and spread-F depletions occur), and accumulates noise characterization and diagnostic data on the dayside. The innovative ETIP sensor design consists of identical paired nadir-viewing far-ultraviolet photometers, which together occupy less volume and footprint than the heritage TIP photometer design and mitigates a long-wavelength contamination issue affecting previous TIP sensors. ETIP operates with a fast off-axis parabolic telescope feeding a heated SrF2 optical blue-cut filter to eliminate undesirable short wavelength emission; a compact CsI photocathode photomultiplier tube, selected for insensitivity to unwanted long wavelength emissions, collects the 135.6 nm emission with extremely high sensitivity (500 counts s-1 Rayleigh-1). By using twin photometers, one unit can monitor ionospheric emission with 100% duty cycle while the other monitors dark counts and/or any residual long-wavelength contaminating (red-leak) emission. When red-leak is negligible, both photometers can collect 135.6 nm emissions, doubling the effective sensitivity to an unprecedented 1000 counts s-1 Rayleigh-1. This sensor design provides uniquely high sensitivity, operational redundancy, and graceful degradation at sensor end-of-life.

Many pulsating phenomena are associated with the auroral substorm. It has been considered that some of these phenomena involve kilometer-scale Alfven waves coupling the magnetosphere and ionosphere. Electric field oscillations at the altitude of the ionosphere are a signature of such wave activity that could distinguish it from other sources of auroral particle precipitation, which may be simply tracers of magnetospheric activity. Therefore, a ground based diagnostic of kilometer-scale oscillating electric fields would be a valuable tool in the study of pulsations and the auroral substorm. In this study we attempt to develop such a tool in the Poker Flat incoherent scatter radar (PFISR). The central result is a statistically significant detection of a 1.4 Hz electric field oscillation associated with a similar oscillating optical emission, during the recovery phase of a substorm. The optical emissions also contain a bright, lower frequency (0.2 Hz) pulsation that does not show up in the radar backscatter. The fact that higher frequency oscillations are detected by the radar, whereas the bright, lower frequency optical pulsation is not detected by the radar, serves to strengthen a theoretical argument that the radar is sensitive to oscillating electric fields, but not to oscillating particle precipitation. Although it is difficult to make conclusions as to the physical mechanism, we do not find evidence for a plane-wave-like Alfven wave; the detected structure is evident in only two of five adjacent beams. We emphasize that this is a new application for ISR, and that corroborating results are needed.

The ionospheric feedback instability (IFI), which involves feedback between ionospheric modifications and waves reflected off the magnetosphere, has up to this point been analyzed in terms of field line integrated (FLI) ionospheric quantities, that is, with the assumption that the ionospheric thickness can be ignored. In this work we test this assumption by solving the two-fluid equations for a representative ionospheric slab of finite thickness. We find that the results are for the most part incompatible with a description in terms of FLI quantities, and that their use can easily lead to an order of magnitude overestimation of the growth rate. This occurs because the first eigenmode, which is the one compatible with an FLI description, is cutoff above a certain frequency, leaving only higher order modes with wavelengths along B that are subsumed by the slab. Taking the results at face value, the parallel electric fields associated with the higher order modes are a possible contributor to electron heating and plasma structure in the E-region ionosphere.

In this paper, we describe the Radio Aurora Explorer (RAX) and its space weather mission. RAX is a satellite mission funded by the National Science Foundation (NSF) to study space weather, and is a joint effort between SRI International and the University of Michigan. The primary mission objective is to study plasma instabilities that lead to magnetic field-aligned irregularities (FAI) of electron density in the lower polar thermosphere (80-400 km). These irregularities are known to disrupt trans-ionospheric communication and navigation signals. The RAX mission will use a network of existing ground radars that will scatter signals off the FAI to be measured by a receiver on the RAX spacecraft. The satellite is a 3kg CubeSat with a scheduled launch in late 2010. RAX is the first of the NSF-sponsored satellites to be manifested for a launch and represents a path forging activity for similar science missions conducted on nanosatellite vehicles.