Extreme ultraviolet observations of the solar corona: First results from the coronal diagnostic spectrometer on SOHO

We present first results from the Coronal Diagnostic Spectrometer (CDS) aboard the ESA/NASA Solar and Heliospheric Observatory (SOHO). CDS is a double spectrometer operating in the 151–785 Å range. This region of the solar spectrum is rich in emission lines from trace elements in the solar atmosphere, which can be used to derive diagnostic information on coronal and transition region plasmas. Early spectra are presented and well identified lines are listed. In addition, examples of images in selected wavelength ranges are shown, for a prominence, a loop system and a bright point, demonstrating well the power of such extreme ultraviolet observations.     

Conversations with Norman Augustine. Interview by Linda Voss

Topics discussed in the interview include trends and economic issues in the aerospace industry, the role of the aerospace industry in national security, and mergers and new ventures in the aerospace industry.     

Space Exploration of Planetary Magnetism

This chapter gives a brief overview of the major observational advances in our quantitative knowledge of the intrinsic magnetic fields of the 8 planets, except Earth, from Mercury to Neptune, since “The Space Age” began on 4 October 1957 with the USSR launching of the world’s first artificial satellite SPUTNIK I.     

Mercury: Magnetic field and interior

Between 1965 and 1975, our knowledge of Mercury and its physical characteristics improved dramatically. Radar studies of the planetary orbit and rotation rate and Mariner 10 spacecraft studies of its surface, atmosphere, magnetic field and plasma environment provided startling new results on what had been the least understood member of the terrestrial planets. With a highly cratered surface and a modest magnetic field, Mercury is a differentiated planet with fractionally the largest iron core of all.     

The Coronal Helium Abundance Experiment on Spacelab 2

The Coronal Helium Abundance Spacelab Experiment, (CHASE), basically consists of a grazing incidence telescope and spectrometer sensitive over the range 150–1335 Å. Whilst aimed primarily at deriving the solar helium abundance from measurements of coronal resonance scattering, its specification has been extended in order to provide a more general purpose solar XUV facility. The instrument will be flown on the Spacelab 2 Mission, currently scheduled for launch in November 1984.Proceedings of the Conference Solar Physics from Space, held at the Swiss Federal Institute of Technology Zurich (ETHZ), 11–14 November 1980.     

Characterisation of residual ionospheric errors in bending angles using GNSS RO end-to-end simulations

Global Navigation Satellite System (GNSS) radio occultation (RO) is an innovative meteorological remote sensing technique for measuring atmospheric parameters such as refractivity, temperature, water vapour and pressure for the improvement of numerical weather prediction (NWP) and global climate monitoring (GCM). GNSS RO has many unique characteristics including global coverage, long-term stability of observations, as well as high accuracy and high vertical resolution of the derived atmospheric profiles. One of the main error sources in GNSS RO observations that significantly affect the accuracy of the derived atmospheric parameters in the stratosphere is the ionospheric error. In order to mitigate the effect of this error, the linear ionospheric correction approach for dual-frequency GNSS RO observations is commonly used. However, the residual ionospheric errors (RIEs) can be still significant, especially when large ionospheric disturbances occur and prevail such as during the periods of active space weather. In this study, the RIEs were investigated under different local time, propagation direction and solar activity conditions and their effects on RO bending angles are characterised using end-to-end simulations. A three-step simulation study was designed to investigate the characteristics of the RIEs through comparing the bending angles with and without the effects of the RIEs. This research forms an important step forward in improving the accuracy of the atmospheric profiles derived from the GNSS RO technique.     

An extension of HZETRN for cosmic ray initiated electromagnetic cascades

Safe and efficient mission operations in space require an accurate understanding of the physical interactions of space radiation. As the primary space radiation interacts with intervening materials, the composition and spectrum of the radiation environment changes. The production of secondary particles can make a significant contribution to radiation exposure. In this work, the NASA space radiation transport code, HZETRN, is extended to include the transport of electrons, positrons, and photons. The production of these particles is coupled to the initial cosmic ray radiation environment through the decay of neutral pions, which produce high energy photons, and through the decay of muons, which produce electrons and positrons. The photons, electrons, and positrons interact with materials producing more photons, electrons and positrons generating an electromagnetic cascade. The relevant cross sections, transport equation, and solution method are introduced. Electron and positron production in Earth’s atmosphere is investigated and compared to experimental balloon-flight measurements. Reasonable agreement is seen between HZETRN and data.     

The MESSENGER Gamma-Ray and Neutron Spectrometer

A Gamma-Ray and Neutron Spectrometer (GRNS) instrument has been developed as part of the science payload for NASA’s Discovery Program mission to the planet Mercury. Mercury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) launched successfully in 2004 and will journey more than six years before entering Mercury orbit to begin a one-year investigation. The GRNS instrument forms part of the geochemistry investigation and will yield maps of the elemental composition of the planet surface. Major elements include H, O, Na, Mg, Si, Ca, Ti, Fe, K, and Th. The Gamma-Ray Spectrometer (GRS) portion detects gamma-ray emissions in the 0.1- to 10-MeV energy range and achieves an energy resolution of 3.5 keV full-width at half-maximum for ⁶⁰Co (1332 keV). It is the first interplanetary use of a mechanically cooled Ge detector. Special construction techniques provide the necessary thermal isolation to maintain the sensor’s encapsulated detector at cryogenic temperatures (90 K) despite the intense thermal environment. Given the mission constraints, the GRS sensor is necessarily body-mounted to the spacecraft, but the outer housing is equipped with an anticoincidence shield to reduce the background from charged particles. The Neutron Spectrometer (NS) sensor consists of a sandwich of three scintillation detectors working in concert to measure the flux of ejected neutrons in three energy ranges from thermal to ∼7 MeV. The NS is particularly sensitive to H content and will help resolve the composition of Mercury’s polar deposits. This paper provides an overview of the Gamma-Ray and Neutron Spectrometer and describes its science and measurement objectives, the design and operation of the instrument, the ground calibration effort, and a look at some early in-flight data.