Forecasting space weather: Predicting interplanetary shocks using neural networks

We are developing a system to predict the arrival of interplanetary (IP) shocks at the Earth. These events are routinely detected by the Electron, Proton, and Alpha Monitor (EPAM) instrument aboard NASA’s ACE spacecraft, which is positioned at Lagrange Point 1 (L1). In this work, we use historical EPAM data to train an IP shock forecasting algorithm. Our approach centers on the observation that these shocks are often preceded by identifiable signatures in the energetic particle intensity data. Using EPAM data, we trained an artificial neural network to predict the time remaining until the shock arrival. After training this algorithm on 37 events, it was able to forecast the arrival time for 19 previously unseen events. The average uncertainty in the prediction 24 h in advance was 8.9 h, while the uncertainty improved to 4.6 h when the event was 12 h away. This system is accessible online, where it provides predictions of shock arrival times using real-time EPAM data.     

EM Transient Protection Requirements for Avionics LRUs

Avionics and electronic equipment installed in aircraft and air breathing missiles are required to operate without upset or damage when subjected to EM environments caused by lightning, NEMP, and Intrasystems transients. To simplify the design effort required to protect electronic equipment and minimize overlapping transient requirements and qualification tests, unified test requirements and procedures are needed. The goal of these unified test procedures would be to insure a known susceptibility level for each newly designed electronic Line Replaceable Unit (LRU). Ten avionics equipments in current Air Force inventory were tested for the purpose of developing unified procedure test methods. Operating LRUs were subjected to transients using common mode cable current (CMCC), groung potentials and chatteriing relay cable injection methods. Based on observed test results and review of current test requirements, test methods and test levels for unified test procedures for power-on transient tests of avionics equipment have been formulated.     

Altimetry,bathymetry and geoid variations at the Gavdos permanent Cal/Val facility

The aim of this work has been to examine the relationship of steep bathymetry in the coastal areas around the permanent Cal/Val facility of Gavdos, and their influence on the produced calibration values for the Jason-2 satellite altimeter. The paper describes how changes in seafloor topography (from 200 to 3500 m depth over a distance of 10 km) are reflected on the determined altimeter parameters using different reference surfaces for satellite calibration. Finally, it describes the relation between these parameter trends and the region’s local characteristics.     

City Noise and Its Effect Upon Airborne Antenna Noise Temperatures at UHF

Results of an experimental program to determine the characteristics of city noise and its effect on airborne UHF antennas are presented. Coherent sources of energy from communications equipment, radar, navigational aids, etc. are not included in the analysis. Based upon the experimental data, a model of the industrial noise is presented in which an industrial area is considered as a uniformly distributed source of independent radiators. The magnitude of the power density distribution was computed to be 3×10-18 to 1×10-18 W/m2/Hz over the UHF band for all the East Coast cities measured, with the exception of New York City which was 5 to 6 dB higher. Relations have been derived and curves plotted to compute antenna noise temperature increase due to city noise, based upon the metropolitan area and its range from the aircraft.     

Radiation measured during ISS-Expedition 13 with different dosimeters

Radiation in low Earth orbit (LEO) is mainly composed of galactic cosmic rays (GCR), solar energetic particles and particles in SAA (South Atlantic Anomaly). The biological impact of space radiation to astronauts depends strongly on the particles’ linear energy transfer (LET) and is dominated by high LET radiation. It is important to measure the LET spectrum for the space radiation field and to investigate the influence of radiation on astronauts. At present, the preferred active dosimeters sensitive to all LET are the tissue equivalent proportional counter (TEPC) and the silicon detectors in various configurations; the preferred passive dosimeters are CR-39 plastic nuclear track detectors (PNTDs) sensitive to high LET and thermoluminescence dosimeters (TLDs) as well as optically stimulated luminescence dosimeters (OSLDs) sensitive to low LET. The TEPC, CR-39 PNTDs, TLDs and OSLDs were used to investigate the radiation field for the ISS mission Expedition 13 (ISS-12S) in LEO. LET spectra and radiation quantities (fluence, absorbed dose, dose equivalent and quality factor) were measured for the space mission with different dosimeters. This paper introduces the role of high LET radiation in radiobiology, the operational principles for the different dosimeters, the LET spectrum method using CR-39 detectors, the method to combine the results measured with TLDs/OSLDs and CR-39 PNTDs, and presents the LET spectra and the radiation quantities measured and combined.     

The X-Ray Spectrometer on the MESSENGER Spacecraft

NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission will further the understanding of the formation of the planets by examining the least studied of the terrestrial planets, Mercury. During the one-year orbital phase (beginning in 2011) and three earlier flybys (2008 and 2009), the X-Ray Spectrometer (XRS) onboard the MESSENGER spacecraft will measure the surface elemental composition. XRS will measure the characteristic X-ray emissions induced on the surface of Mercury by the incident solar flux. The Kα lines for the elements Mg, Al, Si, S, Ca, Ti, and Fe will be detected. The 12° field-of-view of the instrument will allow a spatial resolution that ranges from 42 km at periapsis to 3200 km at apoapsis due to the spacecraft’s highly elliptical orbit. XRS will provide elemental composition measurements covering the majority of Mercury’s surface, as well as potential high-spatial-resolution measurements of features of interest. This paper summarizes XRS’s science objectives, technical design, calibration, and mission observation strategy.     

The Energetic Particle and Plasma Spectrometer Instrument on the MESSENGER Spacecraft

The Energetic Particle and Plasma Spectrometer (EPPS) package on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury is composed of two sensors, the Energetic Particle Spectrometer (EPS) and the Fast Imaging Plasma Spectrometer (FIPS). EPS measures the energy, angular, and compositional distributions of the high-energy components of the in situ electrons (>20 keV) and ions (>5 keV/nucleon), while FIPS measures the energy, angular, and compositional distributions of the low-energy components of the ion distributions (<50 eV/charge to 20 keV/charge). Both EPS and FIPS have very small footprints, and their combined mass (∼3 kg) is significantly lower than that of comparable instruments.     

The Lunar Orbiter Laser Altimeter Investigation on the Lunar Reconnaissance Orbiter Mission

The Lunar Orbiter Laser Altimeter (LOLA) is an instrument on the payload of NASA’s Lunar Reconnaissance Orbiter spacecraft (LRO) (Chin et al., in Space Sci. Rev. 129:391–419, 2007). The instrument is designed to measure the shape of the Moon by measuring precisely the range from the spacecraft to the lunar surface, and incorporating precision orbit determination of LRO, referencing surface ranges to the Moon’s center of mass. LOLA has 5 beams and operates at 28 Hz, with a nominal accuracy of 10 cm. Its primary objective is to produce a global geodetic grid for the Moon to which all other observations can be precisely referenced.