We present the first results from the XMM-Newton Galactic Plane Survey (XGPS). In the first phase of the programme, 22 pointings were used to cover a region of approximately 3 deg 2 between 19• and 22• in Galactic longitude and ±0.6• in latitude. In total we have resolved over 400 point X-ray sources, at 5σ significance, down to a flux limit of ∼2 × 10 −14 erg s −1 cm −2 (2-10 keV). The sources exhibit a very wide range of spectral hardness, with interstellar absorption identified as a major influence. The source populations detected in the soft (0.4-2 keV) band and hard (2-6 keV) band show surprisingly little overlap. The majority of the soft sources appear to be associated with relatively nearby stars with active stellar coronae, judging from their high coincidence with bright stellar counterparts.The combination of the XGPS measurements in the hard X-ray band with the results from earlier surveys carried out by ASCA and Chandra reveals the form of the low-latitude X-ray source counts over 4 decades of flux. It appears that extragalactic sources dominate below ∼10 −13 erg s −1 cm −2 (2-10 keV), with a predominantly Galactic source population present above this flux threshold. The nature of the faint Galactic population observed by XMMNewton remains uncertain, although cataclysmic variables and RS CVn systems may contribute substantially. XMM-Newton observes an enhanced surface brightness in the Galactic plane in the 2-6 keV band associated with Galactic ridge X-ray emission (GRXE). The integrated contribution of Galactic sources plus the breakthrough of extragalactic signal accounts for up to 20 per cent of the observed surface brightness. The XGPS results are consistent with the picture suggested from a deep Chandra observation in the Galactic plane, namely that the bulk of the GRXE is truly diffuse.

An analysis is presented of the soft X-ray background spectrum measured by the EPIC MOS cameras on XMM-Newton in three observations targeted on the North Polar Spur (NPS). Three distinct Galactic plasma components are identified, a cool Local Hot Bubble (LHB) component, Zl0 w 0.1 keV, a cool Galactic Halo component at a similar temperature and a hotter component, Thi -0.26 keV, associated with the NPS itself. Using the new data in combination with the Rosat All-Sky Survey count rates measured in the 0.1-0.4 keV band, we estimate the emission measure of the LHB material to be 0.0040-0.0052 cm-6 pc, which implies an electron density of 0.00&0.011 cm-3 and pressure of -22000 ~r n -~ K. The halo and NPS components lie behind at least 50% of the line-of-sight cold gas for which the total Galactic column density is in the range (2 -8) x 1020 cm-2. Modelling the X-ray emitting superbubble as a sphere at distance 210 pc, radius 140 pc and centre lrr = 352", brr = 15", the implied electron density in the NPS is -0.03 cm-3 with pressure -150000 cm-3 K.The observed spectral line complexes from OVII, OVIII, FeXVII, NeIX, NeX and Mg XI provide constraints on the composition of the plasma. The hot component in the NPS is depleted in oxygen, neon and, to some extent, magnesium and iron. Assuming the effective line of sight across the halo emission is 1 kpc, the electron density in the halo is 0.007-0.011 ~r n -~ and the pressure is N 16500 K, conditions very similar to those in the LHB.

The NASA Radiation Dosimetry Experiment (RaD‐X) stratospheric balloon flight mission obtained measurements for improving the understanding of cosmic radiation transport in the atmosphere and human exposure to this ionizing radiation field in the aircraft environment. The value of dosimetric measurements from the balloon platform is that they can be used to characterize cosmic ray primaries, the ultimate source of aviation radiation exposure. In addition, radiation detectors were flown to assess their potential application to long‐term, continuous monitoring of the aircraft radiation environment. The RaD‐X balloon was successfully launched from Fort Sumner, New Mexico (34.5°N, 104.2°W) on 25 September 2015. Over 18 h of flight data were obtained from each of the four different science instruments at altitudes above 20 km. The RaD‐X balloon flight was supplemented by contemporaneous aircraft measurements. Flight‐averaged dosimetric quantities are reported at seven altitudes to provide benchmark measurements for improving aviation radiation models. The altitude range of the flight data extends from commercial aircraft altitudes to above the Pfotzer maximum where the dosimetric quantities are influenced by cosmic ray primaries. The RaD‐X balloon flight observed an absence of the Pfotzer maximum in the measurements of dose equivalent rate.

Results are presented from evaluations of radiation dosimeters prior to a NASA high‐altitude balloon flight, the RaD‐X mission. Four radiation dosimeters were on board RaD‐X: a Far West Hawk (version 3), a Teledyne dosimeter (UDOS001), a Liulin dosimeter (MDU 6SA1), and a RaySure dosimeter (version 3b). The Hawk is a tissue‐equivalent proportional counter (TEPC) and the others are solid‐state Si sensors. The Hawk served as the “flight standard” and was calibrated for this mission. The Si‐based dosimeters were tested to make sure they functioned properly prior to flight but were not calibrated for the radiation environment in the stratosphere. The dosimeters were exposed to 60Co gamma rays and 252Cf fission radiation (which includes both neutrons and gamma rays) at the Lawrence Livermore National Laboratory (LLNL). The measurement results were compared with results from standard “benchmark” measurements of the same sources and source‐to‐detector distances performed contemporaneously by LLNL calibration facility personnel. For 60Co gamma rays, the dosimeter‐to‐benchmark ratios were 0.84 ± 0.06, 1.07 ± 0.32, 1.31 ± 0.07, and 0.82 ± 0.24 for the TEPC, Teledyne, Liulin, and RaySure, respectively. For 252Cf radiation, the dosimeter‐to‐benchmark ratios were 0.94 ± 0.15, 0.55 ± 0.18, 0.58 ± 0.08, and 0.33 ± 0.12 for the TEPC, Teledyne, Liulin, and RaySure. Some examples of how the results were used to help interpret the flight data are also presented.

Satellite charging is one of the most important risks for satellites on orbit. Satellite charging can lead to an electrostatic discharge resulting in component damage, phantom commands, and loss of service and in exceptional cases total satellite loss. Here we construct a realistic worst case for a fast solar wind stream event lasting 5 days or more and use a physical model to calculate the maximum electron flux greater than 2 MeV for geostationary orbit. We find that the flux tends toward a value of 10 6 cm −2 ·s −1 ·sr −1 after 5 days and remains high for another 5 days. The resulting flux is comparable to a 1 in 150‐year event found from an independent statistical analysis of electron data. Approximately 2.5 mm of Al shielding would be required to reduce the internal charging current to below the National Aeronautics and Space Administration‐recommended guidelines, much more than is currently used. Thus, we would expect many satellites to report electrostatic discharge anomalies during such an event with a strong likelihood of service outage and total satellite loss. We conclude that satellites at geostationary orbit are more likely to be at risk from fast solar wind stream event than a Carrington‐type storm.