J. Klenzing

The NSF Firefly CubeSat mission: Rideshare mission to study energetic electrons produced by lightning

The NSF Firefly CubeSat is a 3U mission designed to perform cutting-edge science, as a secondary payload1,2. Firefly will be the first dedicated mission launched to study Terrestrial Gamma ray Flashes (TGFs), their link to lightning, and their effect in producing energetic electrons that may become stably trapped in the inner radiation belt. Firefly demonstrates the capability of small missions such as CubeSat to do important, focused science, with maximal student involvement, and with a minimal budget and available resources. This presentation will focus on the Firefly mission design, as well as important lessons learned in the development, testing, and design. Future developments in CubeSat-class spacecraft for measurements of energetic radiation will be discussed.

Science of opportunity: Heliophysics on the FASTSAT mission and STP-S26

The FASTSAT spacecraft, which was launched on November 19, 2010 on the DoD STP-S26 mission, carries three instruments developed in joint collaboration by NASA GSFC and the US Naval Academy: PISA, TTI, and MINI-ME.1,2 As part of a rapid-development, low-cost instrument design and fabrication program, these instruments were a perfect match for FASTSAT, which was designed and built in less than one year. These instruments, while independently developed, provide a collaborative view of important processes in the upper atmosphere relating to solar and energetic particle input, atmospheric response, and ion outflow. PISA measures in-situ irregularities in electron number density, TTI provides limb measurements of the atomic oxygen temperature profile with altitude, and MINI-ME provides a unique look at ion populations by a remote sensing technique involving neutral atom imaging. Together with other instruments and payloads on STP-S26 such as the NSF RAX mission, FalconSat-5, and NanoSail-D (launched as a tertiary payload from FASTSAT), these instruments provide a valuable “constellation of opportunity” for following the flow of energy and charged and neutral particles through the upper atmosphere. Together, and for a small fraction of the price of a major mission, these spacecraft will measure the energetic electrons impacting the upper atmosphere, the ions leaving it, and the large-scale plasma and neutral response to these energy inputs. The result will be a new model for maximizing scientific return from multiple small, distributed payloads as secondary payloads on a larger launch vehicle.

The Fixed-Bias Langmuir Probe on the Communication-Navigation Outage Forecast System Satellite: Calibration and Validation

A fixed-bias spherical Langmuir probe is included as part of the Vector Electric Field Instrument (VEFI) suite on the Communication/Navigation Outage Forecast System (C/NOFS) satellite. C/NOFS gathers data in the equatorial ionosphere between 400 and 860 km, where the primary constituent ions are H(+) and O(+). The ion current collected by the probe surface per unit plasma density is found to be a strong function of ion composition. The calibration of the collected current to an absolute density is discussed, and the performance of the spherical probe is compared to other in situ instruments on board the C/NOFS satellite. The application of the calibration is discussed with respect to future fixed-bias probes; in particular, it is demonstrated that some density fluctuations will be suppressed in the collected current if the plasma composition rapidly changes along with density. This is illustrated in the observation of plasma density enhancements on C/NOFS.

Monitoring D-region variability from lightning measurements

In situ measurements of ionospheric D-region characteristics are somewhat scarce and rely mostly on sounding rockets. Remote sensing techniques employing Very Low Frequency (VLF) transmitters can provide electron density estimates from subionospheric wave propagation modeling. Here we discuss how lightning waveform measurements, namely sferics and tweeks, can be used for monitoring the D-region variability and day-night transition, and for local electron density estimates. A brief comparison among D-region aeronomy models is also presented.

PYSAT: Python Satellite Data Analysis Toolkit: PYSAT

R. A. Stoneback, W. B. Hanson Center for Space Sciences, 800 W. Campbell Rd. WT 15, Richardson, TX 75080, USA. (rstoneba@utdallas.edu) A. G. Burrell, W. B. Hanson Center for Space Sciences, 800 W. Campbell Rd. WT 15, Richardson, TX 75080, USA. J. Klenzing, Space Weather Lab / Code 674, Goddard Space Flight Center, Greenbelt, MD, USA M. D. Depew, W. B. Hanson Center for Space Sciences, 800 W. Campbell Rd. WT 15, Richardson, TX 75080, USA.

Ram/Wake and Surface Layer Effects on DC Electric Field Measurements in LEO

The USAF Communication/Navigation Outage Forecast System satellite, launched into an eccentric low earth orbit (401 km perigee by 867 km apogee) of 13° inclination on April 16, 2008, has a set of dc electric field probes that constitute part of the Vector Electric Field Investigation (VEFI). In order to obtain the ambient electric field, the v×B component of electric field must be subtracted from the VEFI measurements. After this subtraction and the subtraction of the ambient dc electric components, a residual dc offset directed toward the spacecraft wake is still observed, which varies somewhat within an orbit and on longer timescales. One of the interesting features of these offsets is that when the satellite is occasionally rotated, the offsets are reset to their baseline values, only to come back within a month or so. Various hypotheses have been proposed to explain the residual dc offsets. In this paper, we explore the possibilities that either the influence of the spacecraft wake on the sensors or that modified surface layers on the probe surfaces are producing the offsets. Nascap-2k and EWB models are used to show the various influences of the wake and of surface materials. Finally, a hypothesis is produced that quantitatively explains many of the salient features of the offsets. The feasibility of using dc electric field probes in space is reaffirmed. Recommendations for probe construction on future spacecraft to ameliorate spurious effects are presented.

Multi-instrument observations of an MSTID over Arecibo Observatory

The Penn State All-Sky Imager (PSASI) at Arecibo Observatory provides planar horizontal context to the vertical ionospheric profiles obtained by the Incoherent Scatter Radar (ISR). Electric field measurements from the Communication/Navigation Outage Forecast System (C/NOFS) satellite are mapped down geomagnetic field lines to the height of the airglow layer, allowing multi-instrument studies of field-aligned irregularities with radar, imager, and satellite. A Medium-Scale Traveling Ionospheric Disturbance (MSTID) was observed during such a conjunction near the December solstice of 2009.

VLF and HF plasma waves associated with spread-F plasma depletions observed on the C/NOFS satellite

The C/NOFS spacecraft frequently encounters structured plasma depletions associated with equatorial spread-F along its trajectory that varies between 401 km perigee and 867 km apogee in the low latitude ionosphere. We report two classes of plasma waves detected with the Vector Electric Field Investigation (VEFI) that appear when the plasma frequency is less than the electron gyro frequency, as is common in spread-F depletions where the plasma number density typically decreases below 104/cm3. In these conditions, both broadband VLF waves with a clear cutoff at the lower hybrid frequency and broadband HF waves with a clear cutoff at the plasma frequency are observed. We interpret these waves as “hiss-type” emissions possibly associated with the flow of suprathermal electrons within the inter-hemispherical magnetic flux tubes. We also report evidence of enhanced wave “transients” sometimes embedded in the broader band emissions that are associated with lightning sferics detected within the depleted plasma regions that appear in both the VLF and HF data. Theoretical implications of these observations are discussed.

DC electric fields, associated plasma drifts, and irregularities observed on the C/NOFS satellite

Results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. Compared to data obtained during more active solar conditions, the ambient DC electric fields and their associated E × B drifts are variable and somewhat weak, typically < 1 mV/m. Although average drift directions show similarities to those previously reported, eastward/outward during day and westward/downward at night, this pattern varies significantly with longitude and is not always present. Daytime vertical drifts near the magnetic equator are largest after sunrise, with smaller average velocities after noon. Little or no pre-reversal enhancement in the vertical drift near sunset is observed, attributable to the solar minimum conditions creating a much reduced neutral dynamo at the satellite altitude. The nighttime ionosphere is characterized by larger amplitude, structured electric fields, even where the plasma density appears nearly quiescent. Data from successive orbits reveal that the vertical drifts and plasma density are both clearly organized with longitude. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. The VEFI data represents a new set of measurements that are germane to numerous fundamental aspects of the electrodynamics and irregularities inherent to the Earths low latitude ionosphere.