The oriented scintillation spectrometer experiment for the gamma-ray observatory

The Oriented Scintillation Spectrometer Experiment (OSSE) for the Gamma Ray Observatory is described. OSSE uses four identical NaI(T1)-CsI(Na) phoswich detectors to provide gamma-ray line and continuum detection capability in the 0.05–10 MeV energy range. Additional gamma-ray and neutron detection capability is achieved above 10 MeV. Each detector has a CsI annular shield and a tungsten alloy collimator which define a 5° × 11° (FWHM) field-of-view. The detectors have independent, single-axis orientation systems which permit offset pointing to provide source-background subtraction. The sensitivity for line gamma rays in the 0.05–10 MeV region will be 2–3 × 10^?5 photons/cm²-s for a 10⁶-second observation period. The several modes of data acquisition and the emphases for the planned observational program are discussed.     

The POKER experiment: A 10,800 cm2 MWPC's array payload for hard X-Ray Astronomy

In this paper the POKER-HXR81M hard X-Ray payload is described. The instrument, designed and built at the Istituto di Astrofisica Spaziale of Frascati, is a very large array of MultiWire Proportional Counters (MWPC) devoted to stratospheric observations of cosmic sources in the field of hard X-Ray Astronomy. The payload basically consists of four passively collimated MWPC's having a geometric sensitive area of 2,700 cm² each with an efficiency higher than 10% in the operative range 15–200 KeV (80% at 60 KeV) with a square field of view of 5° × 5° FWHM. The overall spectral resolution is 13% at 60 KeV. The four MWPC's are filled with a very pure gas mixture of Xenon-Argon-Isobuthane at high pressure (3 bars).This experiment has been successfully flown during summer 1981 from the Milo balloon facility (Sicily, Italy). The performances of the payload and the preliminary results obtained during the 17 hours flight are discussed.     

The scaler mode in the Pierre Auger Observatory to study heliospheric modulation of cosmic rays

The impact of the solar activity on the heliosphere has a strong influence on the modulation of the flux of low energy galactic cosmic rays arriving at Earth. Different instruments, such as neutron monitors or muon detectors, have been recording the variability of the cosmic ray flux at ground level for several decades. Although the Pierre Auger Observatory was designed to observe cosmic rays at the highest energies, it also records the count rates of low energy secondary particles (the scaler mode) for the self-calibration of its surface detector array. From observations using the scaler mode at the Pierre Auger Observatory, modulation of galactic cosmic rays due to solar transient activity has been observed (e.g., Forbush decreases). Due to the high total count rate coming from the combined area of its detectors, the Pierre Auger Observatory (its detectors have a total area greater than 16,000 m²) detects a flux of secondary particles of the order of ∼10⁸ counts per minute. Time variations of the cosmic ray flux related to the activity of the heliosphere can be determined with high accuracy. In this paper we briefly describe the scaler mode and analyze a Forbush decrease together with the interplanetary coronal mass ejection that originated it. The Auger scaler data are now publicly available.     

Detection of the high energy component of Jovian electrons in Low Earth Orbit with the PAMELA experiment

The PAMELA experiment is devoted to the study of cosmic rays in Low Earth Orbit with an apparatus optimized to perform a precise determination of the galactic antimatter component of c.r. It is constituted by a number of detectors built around a permanent magnet spectrometer. PAMELA was launched in space on June 15th 2006 on board the Russian Resurs-DK1 satellite for a mission duration of 3 years. The characteristics of the detectors, the long lifetime and the orbit of the satellite, will allow to address several aspects of cosmic-ray physics. In this work we discuss the observational capabilities of PAMELA to detect the electron component above 50 MeV. The magnetic spectrometer allows a detailed measurement of the energy spectrum of electrons of galactic and Jovian origin. Long term measurements and correlations with Earth–Jupiter 13 months synodic period will allow to separate these two contributions and to measure the primary electron Jovian component, dominant in the 50–70 MeV energy range. With this technique it will also be possible to study the contribution to the electron spectrum of Jovian e⁻ reaccelerated up to 2 GeV at the Solar Wind Termination Shock.     

Far-infrared and submillimeter survey of the galactic center and nearby galactic plane

Maps are presented with 12′ resolution of the Galactic Center and adjacent galactic plane, from ?^II = 359° to ?^II = 5°. The data were obtained with the Steward Observatory cryogenically-cooled, balloon-borne telescope. The data are from channels filtered for a bandpass of 70 μm < γ < 110 μm and for a longpass of γ > 80 μm. For the typical effective temperature of 25 K of a galactic HII region at this spatial resolution, the effective wavelength of the channels are 93 μ and 145 μm. Continuous emission is mapped along the galactic plane in both wavelengths. There are two contrasts between the immediate vicinity of SgrA (?^π < 1°) and the galactic plane in general. Firstly, for ?^π > 1° the galactic plane narrows dramatically at 93 μm, while retaining its width at 145 μm. Secondly, the individual sources at ?^π > 1° (which we associate with HII regions) have greater peak brightness in the 145 μm channel than the 93 μm channel, while SgrA hasapproximately equal peak brightness in each. The maps demonstrate the importance of submillimeter wavelengths to galactic surveys.     

Thermal net flux measurements on the pioneer Venus entry probes

Corrected thermal net radiation measurements from the four Pioneer Venus entry probes at latitudes of 60°N, 31°S, 27°S, and 4°N are presented. Three main conclusions can be drawn from comparisons of the corrected fluxes with radiative transfer calculations: (1) sounder probe net fluxes are consistent with the number density of large cloud particles (mode 3) measured on the same probe, but the IR measurements as a whole are most consistent with a significantly reduced mode 3 contribution to the cloud opacity; (2) at all probe sites, the fluxes imply that the upper cloud contains a yet undetected source of IR opacity; and (3) beneath the clouds the fluxes at a given altitude increase with latitude, suggesting greater IR cooling below the clouds at high latitudes and water vapor mixing ratios of about 2–5×10^?5 near 60°, 2–5×10^?4 near 30°, and >5×10^?4 near the equator.     

Dosimetric investigations on Mars-96 mission.

The dosimetric experiments Dose-M and Liulin as part of the more complex French-German-Bulgarian-Russian experiments for the investigation of the radiation environment for Mars-96 mission are described. The experiments will be realized with dosemeter-radiometer instruments, measuring absorbed dose in semiconductor detectors and the particle flux. Two detectors will be mounted on board the Mars-96 orbiter. Another detector will be on the guiderope of the Mars-96 Aerostate station. The scientific aims of Dose-M and Liulin experiments are: Analysis of the absorbed dose and the flux on the path and around Mars behind different shielding. Study of the shielding characteristics of the Martian atmosphere from galactic and solar cosmic rays including solar proton events. Together with the French gamma-spectrometer and the German neutron detectors the investigation of the radiation environment on the surface of Mars and in the atmosphere up to 4000 m altitude will be conducted.     

The PAMELA Storage and Control Unit

The PAMELA experiment aims to measure with great precision the antimatter present in our Galaxy in the form of high energy particles; in the same time it will measure the galactic, solar and trapped components of cosmic rays. The experiment will be housed on board a Russian Resurs-DK1 satellite and launched in the year 2005 to fly a 350–600 km orbit with an inclination of 70.4°. All operations of the instrument – including data storage – are handled by the PAMELA Storage and Control Unit (PSCU), which is divided in a Central Processing Unit (CPU) and a Mass Memory (MM). The CPU of the experiment is based on a ERC-32 architecture (a SPARC v7 implementation) running a real time operating system (RTEMS). The main purpose of the CPU is to handle slow control, acquire and store data on a 2 GB MM. Communications between PAMELA and the satellite are performed via a 1553B bus. Data acquisition from the sub-detectors (Time-of-Flight counter, Magnetic Spectrometer, Electromagnetic Calorimeter, Anticoincidence shield, Neutron Detector, and Bottom scintillator S4) is performed via a 2 MB/s interface. Download from the PAMELA MM towards the satellite main storage unit is handled by a 16 MB/s bus. The daily amount of data transmitted to ground has been evaluated in not more 20 GB. In this work, we describe the CPU of the experiment and the general software scheme.     

Observed solar cycle modulation of galactic cosmic rays over a range of rigidities

We have studied the long-term, steady-state, solar cycle modulation of galactic cosmic ray intensity for seven cycles (17–23). Our analysis is based on the data obtained with a variety of detectors on earth (neutron monitors of the global network and muon detectors) as well as telescopes flown on high altitude balloons and on-board near-earth satellites. The median rigidity of response for these detectors to galactic cosmic ray spectrum lies in the range 1–70 GV. We correlate cosmic ray data to sunspot numbers, Ap, solar wind bulk speed (V), magnetic field (B), as well as to the cycle maximum (M), minimum (m), and the epochs of the solar polar field reversals. This enables us to derive the rigidity dependence of observations, and helps us to define the characteristics of the modulation function in the heliosphere.     

A large area multitechnique experiment for hard X-ray astronomy

A balloon-borne multitechnique large area experiment consisting of 2 co-aligned detectors (3200 cm² NaI and 1800 cm² multiwire proportional counters), is described, which is capble of producing observations of the hard X-ray sky with very high sensitivity and good spectral resolution over the whole operative range (15–300 keV).     

Evidence for a 2200 km extended wave system at the mesopause level

A panoramic view of the nightglow atmospheric emission in the 780–1000 nm spectral range is constructed using CCD images taken at the Pic de Châteaurenard (Altitude 2989 m, Hautes-Alpes) on July 14–15, 1999. A set of 28 images each having a 36° × 36° field of view is assembled to form a panorama covering 360° in azimuth and extending from the horizon to the zenith. Each photograph is processed in order to invert the perpective effect assuming that the emission comes from a thin layer located at the altitude of 85 km. The effect of refraction is calculated and taken into account. The stars are removed using a numerical filter. The inverted panorama appears as a disk having a radius equal to 1100 km. It is comparable to a satellite view of the emissive layer. A wave system extends in the W-NW to E-SE direction over more than 2200 km. A second set of 30 successive images of the same field of view taken on May 18–19, 1998 is used to determine the wave parameters. The main horizontal wavelength is equal to 42 km and the horizontal phase velocity has a value of 40 ± 2 m.s⁻¹. The images show that the atmospheric OH emission is a tracer of the dynamics of the atmosphere at the level where the excited OH radicals are produced. The OH* radical population depends upon its quenching by O, O₂ and N₂. As a result, the emission intensity is a function of the air temperature and density which are subject to variations due to gravity and windshear waves and other dynamic processes such as tides and turbulence.     

Exosat observations of the galactic bulge X-ray source GX17+2

We have measured the X-ray flux of the bright galactic bulge source GX17+2 in the energy range 1–20 keV using the EXOSAT ME experiment. During 8 hours of continuous observation an X-ray flare was observed (lasting ～1 hr) followed by an intensity increase. The data show intensity dips with a quasiperiod of ～1.4 hours and quasi-periodic oscillations on time scale of 200–500 sec, which are possibly connected with oscillations of an accretion disc. The spectrum can be fitted by two blackbody spectra with kT₁～1keV, and kT₂～2keV, respectively, and an iron line at 6.3 ± 0.3 keV having 130 eV equivalent width. While the low energy component is rather stable, the 2keV-component shows considerable intensity variations. We suggest that the latter component represents emission from the inner part of the accretion disc while the soft spectrum is blackbody emission from the surface of the neutron star.     

A directional gamma-ray telescope using coded aperture techniques

A directional detector for γ-ray astronomy has been developed to image sources in the energy range 0.1 to 5 MeV. An array of 35 gain stabilized bismuth germanate detectors, together with a coded aperture mask based on a Uniformly Redundant Array (URA), allows imaging in 4° square sky bins over a 16° X 24° field-of-view. The position of a strong point source, such as the Crab Nebula, can be determined to within ?1°. A complementary “anti-mask” greatly reduces systematic effects arising from non-uniform background rates amongst the detectors. The telescope has an effective area of 190 cm² and an energy resolution of 19.5% FWHM at 662 keV. Results of laboratory tests of the imaging system, including the ability to image multiple sources, uniformity of response over the field-of-view, and the effect of the “anti-mask”, are in good agreement with computer simulations. Features of the flight detector system are described and results of laboratory tests and computer simulations are reviewed. A balloon flight of the telescope is planned for the fall of 1982.     

Equatorial secondary cosmic ray observatory to study space weather and terrestrial events

Recently, equatorial secondary cosmic ray observatory has been established at Equatorial Geophysical Research Laboratory (EGRL), Tirunelveli, (Geographic Coordinates: 8.71°N, 77.76°E), to study secondary cosmic rays (SCR) produced due to the interaction of primary cosmic rays with the Earth’s atmosphere. EGRL is a regional center of Indian Institute of Geomagnetism (IIG), located near the equator in the Southern part of India. Two NaI(Tl) scintillation detectors are installed inside the temperature controlled environment. One detector is cylindrical in shape of size 7.62?cm?×?7.62?cm and another one is rectangular cuboid of 10.16?cm?×?10.16?cm?×?40.64?cm size. Besides NaI(Tl) detectors, various other research facilities such as the Geomagnetic observatory, Medium Frequency Radar System, Digital Ionosonde, All-sky airglow imager, Atmospheric electricity laboratory to measure the near-Earth atmospheric electric fields are also available at EGRL. With the accessibility of multi- instrument facilities, the objective is set to understand the relationship between SCR and various atmospheric and ionospheric processes, during space weather and terrestrial events.For gamma-ray spectroscopy, it is important to test the performance of the NaI(Tl) scintillation detectors and to calibrate the gamma-ray spectrum in terms of energy. The present article describes the details of the experimental setup installed near the equator to study cosmic rays, along with the performance testing and calibration of the detectors under various conditions. A systematic shift in the gain is observed with varying temperature of the detector system. It is found that the detector’s response to the variations in the temperature is not just linear or non-linear type, but it depends on the history of the variation, indicating temperature hysteresis effects on NaI detector and PMT system. This signifies the importance of isothermal environment while studying SCR flux using NaI(Tl) detectors, especially for the experiments conducted during daytime such as solar eclipses etc.     

Spatial asymmetry in topside ion density and vertical E × B plasma drift velocity within 75°E–95°E

The ion density measured by the Ionospheric Plasma and Electrodynamics Instrument (IPEI) on board the ROCSAT -1 over the 75°E and 95°E meridian at 600km altitude has been utilized to examine the latitudinal and longitudinal distribution within the Indian sector, in particular, the north-south and east-west asymmetries of the equatorial ionization anomaly (EIA). A longitudinal gradient in ion density at 600?km higher towards 95°E develops during the noontime and afternoon hours when the EIA is at its peak. The density gradient persists till evening hours when pre-reversal enhancements occur. The vertical E?×?B plasma drift velocity measured simultaneously by ROCSAT -1 for the same space-time configuration has also been studied. In addition to diurnal, seasonal and solar activity variations in E?×?B drift velocity, the longitudinal gradient is also observed. The EIA at the altitude of 600?km peaks at different latitudes and are mostly asymmetric about the magnetic equator. From midnight till 0800 LT, the ion density across the equator is nearly uniform in the equinoxes. But in the solstices, the density exhibits a north-south gradient. In the June solstice, density is higher in the northern hemisphere and decreases gradually towards south. The gradient in density reverses in December solstice. Normally, the EIA peaks within 1200 LT and 1600 LT while around 2000 LT, pre-reversal enhancement of ionization occurs affecting the EIA evening structure. The strength of the EIA also exhibits seasonal, year-to-year and hemispheric variations. The longitudinal asymmetry of drift velocity along 75°E and 95°E longitude sectors is the contributing factor behind the observed longitudinal asymmetry in ion density. Significant positive correlation between the strength of the EIA and E?×?B drift is observed in both longitudes.     

Some features of the day-to-day MLT wind variability in winter 2017–2018 as seen with a European/Siberian meteor radar network

We present results of wind measurements near the mesopause carried out with meteor radars (MRs) at Collm (51°N, 13°E), Obninsk (55°N, 37°E), Kazan (56°N, 49°E), Angarsk (52°N, 104°E) and Anadyr (65°N, 178°E) from October 1, 2017 till March 31, 2018. The Collm and Kazan MRs are SKiYMET radars with vertical transmission and radio echo height finding, while the other radars operate with horizontal transmission and without height finding. We paid particular attention to the meridional wind variability with periods of 4–6 days and 9–11 days. The waves with these periods are seen as spots of the wave activity in the wavelet spectra and include oscillations with different periods and different discrete zonal wavenumbers. These wave packets successively propagate as a group of waves from one site to another one in such a way that they are observed at one site and almost disappear at the previous one. The 4–6 wave group includes planetary-scale oscillations (individual spectral components) which have eastward phase velocities and mostly zonal wavenumbers 2 and 3, and the vertical wavelength exceeds 70 km at middle latitudes. The source of the oscillations is the polar jet instability. The wave group itself propagates westward, and the amplitudes of wind oscillations are approximately 5–6 m/s as obtained from the wind data averaged over the meteor zone. The 9–11 day wave set propagates westward as a group and mainly consists of spectral components which have westward phase velocity and zonal wavenumber 1. Amplitudes of these wind perturbations strongly vary from station to station and can reach, approximately, 8 m/s. The vertical wavenumber is 0.014 km⁻¹ as taken from the Kazan and 0.05 km⁻¹ according to the Collm data. We obtained a global view on the waves by using the AURA MLS geopotential data. We found a good correspondence between wave features obtained from the MR wind measurements and the MLS data. To our knowledge, such a wave propagation of planetary wave in the mesosphere/lower thermosphere (MLT) region has so far not obtained much attention.     

The Magellan project

Magellan is one of the future space projects being studied by the European Space Agency. The aim is to provide high resolution (λ/Δλ ≥ 2.5 × 10⁴) spectra in the far and extreme UV (between 500 and 1550 Å) of faint galactic and extragalactic objects (V ≤ 16^m). The instrument consists of a mechanical collimator, a concave holographic grating and a bidimensional photon-counting detector. A low resolution mode (λ/Δλ ≥ 10³) will provide spectra of objects as faint as 18^m.5. Magellan is planned as an observatory, operated in real time, and allowing interaction with the observer.     

Co-registration of Chang’E-1 stereo images and laser altimeter data with crossover adjustment and image sensor model refinement

Topographic information is of fundamental importance for various scientific investigations in lunar and planetary exploration. To provide high-precision, seamless mapping capability, it is critical to co-register image and altimetry data, the two major data sources for topographic modeling. This paper presents a method for co-registration of Chang’E-1 (CE-1) stereo images and laser altimeter (LAM) data with crossover adjustment and refinement of the image sensor model. The crossover adjustment is tested in a larger area (0–60°N, 50–0°W); the image refinement and co-registration with LAM data are tested in an area (46.2–50.0°N, 31.8–28.8°W) within the larger area. Experimental results demonstrate that this co-registration reduces the mean differences of inconsistency from more than 200 m to just 3.21 m in the Z direction of object space. In image space, the mean errors of homologous points both in the column and row directions are reduced to below 0.1 pixel. This indicates that the proposed crossover adjustment of LAM data and refinement of the CE-1 stereo image model can effectively improve co-registration of the two data sets.     

FIGARO: An experiment for pulsar and variable source studies in the MeV range

We present a large area, balloon borne, NaI(Tl) detector for low-energy gamma rays with temporal signature : FIGARO.The main detector is a mosaic of 12 NaI(Tl) tiles 22.5 × 15 × 5 cm, for a total geometric area of 4050 cm².In the energy band 140 keV - 6 MeV, the expected background counting rate at float altitude is in the range of two to three thousands counts per second.For pulsar analysis the expected 3δ sensitivity for 5 hours exposition time is 2.5 10^?4 ph/cm².s.MeV (150–500 keV) 1.5 10^?4 ph/cm².s.MeV (1–6 MeV). This performance, together with the large effective area and the relatively short duration of a balloon flight, make FIGARO particularly suitable for the identification of sources by means of temporal analysis.For objectives in the Northern sky, including the Crab pulsar, a transmediterranean flight is planned for the summer of 1982 ; a Southern mission is scheduled in Brazil for the fall of 1983 (Vela, PSR 1822-09).     

Energy deposition in the polar ionosphere as determined by measurements aboard ‘INTERCOSMOS-BULGARIA-1300’ satellite

Data were obtained from the measurements of optical emissions, ion drift, DC magnetic field and energetic particles, on board INTERCOSMOS - BULGARIA - 1300 satellite. In two cases of night-time passes through auroral oval, an estimate has been made of the energy input by particle precipitation and Joule heating. In order to determine the Joule heating, the Pedersen currents flowing in the lower ionosphere were determined. In orbits 231 and 203 Pedersen currents of 0.94 Am^?1 and 0.71 am^?1 were observed. From these values estimates of Joule heating rates of2 × 10^?7Wm^?3 and8 × 10^?7Wm^?3 were obtained. The integral energy deposited by the precipitated particles was also estimated in the current systems regions. The possibility for identification of the auroral electrojet based only on satellite data is pointed out.