EUVITA — An extreme UV imaging telescope array with spectral capability

EUVITA is a set of 8 extreme UV normal incidence imaging telescopes, each of them sensitive in a narrow band (λ/Δλ = 15 to 80), centered at wavelengths between 50 and 175 Å. Each telescope has an effective area of a few cm²; a field of view of 1.2° and a spatial resolution of 10 arcsec.

EUVITA will be flown on the Russian mission SPECTRUM X-G. This satellite will be launched in a highly eccentric orbit with a period of 4 days, allowing long, uninterrupted observations (e.g. 10⁵ seconds). EUVITA's narrow spectral bands allow the measurement of source parameters such as temperature or power law index as well as interstellar absorption, and will resolve groups of strong lines emitted by optically thin hot plasmas.     

A Far Infrared Photometer (FIRP) for the Infrared Telescope in Space (IRTS)

We describe the design and calibration of the Far-Infrared Photometer (FIRP), one of four focal plane instruments on the Infrared Telescope in Space (IRTS). The FIRP will provide absolute photometry in four bands centered at 150, 250, 400, and 700 μm with spectral resolution λ/Δλ ≈ 3 and spatial resolution ΔΘ = 0.5 degrees. High sensitivity is achieved by using bolometric detectors operated at 300 mK in an AC bridge circuit. The closed-cycle ³He refrigerator can be recycled in orbit. A 2 K shutter provides a zero reference for each field of view. More than 10% of the sky will be surveyed during the ≈3 week mission lifetime with a sensitivity of <10⁻¹³ W·cm⁻²·sr⁻¹ per 0.5 degree pixel.     

UV photobiochemistry of anhydrobiotic organisms at extremely low temperatures

Spores of Bacillus subtilis (TKJ 3412), cells of Deinococcus radiodurans R₁ (wild type) and conidia of Aspergillus ochraceus (strain 3174) have been UV irradiated (254 nm) in the dry state (3% relative humidity, argon) or in aqueous suspension at room temperature, at −55°C to −70°C and at −165°C to −170°C. The following effects have been analyzed: decrease in viability, occurrence of DNA strand breaks (pulsed-field gel electrophoresis) and production of DNA-protein cross-links (membrane filter method). The loss in viability is usually more pronounced at around −70°C than at room temperature, but it is lowest around −170°C. The kind of prevailing DNA damage varies from organism to organism. The amount of UV induced DNA-protein cross-link products steadily decreases with the temperature and is lowest at −170°C. The decrease in highly polymeric DNA by double strand breaks follows no universal pattern. The observed hypersensitivity of the three very different species at −70°C can therefore not be simply explained on the basis of the number of DNA lesions analyzed in the course of this work. We suggest that also the changing state of cellular water below and above about −130°C significantly contributes to the change in photosensitivity.     

Simulation experiments of the cosmic ray isotope telescope on ETS VI

A computer simulation was carried out to evaluate the basic characteristics of a Δ E×E cosmic ray telescope consisting of 23 solid state detectors including 3 position sensitive detectors with large effective area. Based on the simulation, the geometric factor of the telescope is deduced to be as large as 22.5 cm²sr, almost independent of charge and energy concerned. The energy ranges to be covered by the telescope are, for example, 18–98 MeV/n for Li and 56–339 MeV/n for Fe. By analyzing simulated data, the mass resolution for iron in the overall energy range covered by the telescope is estimated as about 0.22 amu in standard deviation. The expected counting rates and mass-histograms are simulated for Galactic cosmic rays and solar energetic particles.     

Wide field ultraviolet observations of Comet Halley with the FAUST Spacelab I instrument

The wide field (7.5°), arc minute imaging, and spectroscopic capabilities of the Far Ultraviolet FAUST telescope which will be flown on Spacelab I can provide valuable information on Comet Halley. The use of the FAUST instrument in obtaining images of the hydrogen coma at 1216 Å, and in obtaining objective grating spectroscopy from 1300–3300 Å of the comet and tail, are described. The FAUST images would provide large field of view data that are required for model calculations of gas production rates and the determination of scale lengths and lifetimes of ion species.     

Geminga pulsar observations with gamma-telescope Gamma-1

The Geminga light curve obtained with the “Gamma-1” telescope features two peaks separated by 0.5 ± 0.03 period. The light curve is pronounced for γ-quanta energies higher than 400 MeV. The pulsed flux upper limit (1σ) in the energy interval 50 – 300 MeV is 6·10⁻⁷ cm⁻²sec⁻¹. For energies >300 MeV the pulsed component power law spectrum has an exponent 1.1 _−0.3^+1.1 and an integral flux (1.1±0.3)·10⁻⁶ cm⁻²sec⁻¹.     

CMB anisotropy testing from small satellites

We review the advantages and possibilities of small satellites. New results of data reduction of the satellite-borne experiment RELICT-1 are presented. For the inflation spectrum of primordial perturbations we obtained the estimate for quadrupole component 6·10⁻⁶ <ΔT₂/T<3.3·10⁻⁶. The RELICT-2 mission will provide a possibility of measurement of CBR anisotropy down to the level less than ΔT₂/T = 10⁻⁸. We present the results of engineering testing of RELICT-2 measurement system and discuss ways of improving of the radiometers sensitivities.     

Numerical simulations of the radiance from the comet 46P/Wirtanen in the various configurations of the measurements during “Rosetta” mission

The work we present deals with the spectrometric measurements of VIRTIS instrument of the Comet P/Wirtanen planned for the Rosetta mission. This spectrometer can monitor (VIRTIS M channel: 0.250μm – 0.980μm; Δκ=20cm⁻¹; 0.980 – 5.0 μm; Δκ = 5cm⁻¹; VIRTIS H channel: 2.0 μm – 5.0 μm; Δκ=2cm⁻¹) the nucleus and the coma in order to provide a general picture of coma's composition, the production of gas and dust, the relationship of coma production to surface composition and the structure and variation of mineralogy of the nucleus surface. During the mission the observation conditions of the spectroscopic investigation change due to different relative positions spacecraft/comet, and to the different illumination conditions of the surface at various distances of the comet to the Sun. The nucleus surface is continuously modified by the ice sublimation accompanied by gas and dust emission. Consequently the surface also its spectrophotometric properties changes and their monitoring can give a new insight. The important role of simulations is to predict the results of measurements in various experimental condition what, in the future, can help in interpretation of the measured data.

In this paper the first results of our simulation the radiance from the comet in the 0.25–5.0μm spectral range at two distances from the Sun (1AU and 3AU) are shown. The distance between the Rosetta orbiter and the nucleus surface as well as the sun zenith angles are taken into account according to the Rosetta mission phases. In fact the surface and coma properties vary along the comet orbit, and should be taken into account in our calculations. The optical parameters of the dust on the surface (e.g. reflectance) and in the coma (e.g. Q_ext) were calculated from optical constants of possible comet analogues. The thermodynamic parameters of the comet are taken from the models of comet evolution. Through this kind of modelling it is possible to identify the surface characteristics in spectra of the radiation from the surface of nucleus transmitted through the coma loaded with dust and gases.

Even if the “Rosetta mission” is postponed, with the consequence of a target change, we think that our idea and the method used for the simulations can be useful also for the new Rosetta target - the comet 67P/Churyumov Gerasimenko.     

Geotropic sensitivity exhibited by single hornets: The influence of caste, age, light and temperature

Hornet ( , Hymenoptera: Vespinae) workers, queens and males, aged 0–24 hours (i.e. juveniles) and 24 hours and more (i.e. adults) were tested for their responses to changes in the direction of the gravitational force while placed on a flat surface gradually tilted between 0.5° and 180°. The tests were run on non-blind and blind hornets, at temperatures ranging between 18°C and 35°C, in daylight as well as in the dark. Up to 18 hours of age, negative phototaxis prevailed among the hornets, which displayed a clear preference for remaining in the dark regardless of the geotropic position. Between 18–24 hours of age, there was gradual appearance of a sensitivity to change in the geotropic position. Above 24 hr of age, the hornets became sensitive to changes in their declinations, with workers becoming sensitive at a 3–5° declination, queens at 4–5° and males at a declination of 8–19° from the horizontal. Hornet response takes the form of an upward climb, to the highest point of the test surface. Such response required a temperature exceeding 24.8–25°C for workers, 23.2°C for queens and 20.8–21°C for males.     

High spectral resolution Fabry-Perot interferometer measurements of comet Halley at H-alpha and 6300 Å

A 40.6 cm Newtonian telescope has been interfaced to the Fabry-Perot interferometer at the Arecibo Observatory to make high spectral resolution measurements of Comet Halley emissions at 6562.72 Å (H-alpha) and 6300.3 Å (OI). In March 1986 the H-alpha surface brightness for a 5′.9 field of view centered on the comet nucleus decreased from 39±7.8 rayleighs on 12 March to 16±3.8 rayleighs on 23 March. The atomic hydrogen production rate on 12 March 1986 was 1.62±0.5 × 10³⁰ s⁻¹, and on 23 March 1986 it was 6.76±2.3 × 10²⁹ s⁻¹. Using spectral resolution of 0.196 Å, we found the atomic hydrogen outflow velocity to be approximately 7.9±1.0 km s⁻¹. In general, the H-alpha spectra are highly structured, and indicative of a multiple component atomic hydrogen velocity distribution. An isotropic outflow of atomic hydrogen at various velocities is not adequate to explain the spectra measured at H-alpha. The 6300.3 Å emission of O(1D) had a surface brightness of 81±16 rayleighs on 15 March 1986, and 95±11 rayleighs on 17 March 1986. After adjustment for atmospheric extinction, the implied O(1D) production rate on 15 March is 6.44±3.0 × 10²⁸ s⁻¹, and the production rate on 17 March is 5.66±2.7 × 10²⁸ s⁻¹. These spectra included a feature at 6300.8 Å that we attribute to NH₂. The brightness of this emission feature was 37±11 rayleighs on 15 March.     

Towards validation of SCIAMACHY lunar occultation NO2 vertical profiles

Vertical profiles of stratospheric nitrogen dioxide (NO₂) have been retrieved from moderate resolution lunar occultation transmission spectra measured by Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on board the European Environmental Satellite (ENVISAT). These measurements were taken over the high southern latitude of 50°–90° during the period of 2003–2005. To assess the accuracy of the retrieved NO₂ profiles, the SCIAMACHY nighttime NO₂ profiles were compared with NO₂ profiles retrieved from sunrise solar occultation spectra measured by the Halogen Occultation Experiment (HALOE) and the Stratospheric Aerosol and Gas Experiments II (SAGE II) using a photochemical correction model. The validation results show good agreement of SCIAMACHY lunar occultation NO₂ with scaled HALOE and SAGE II profiles. The relative mean differences (rmd) with scaled HALOE profiles are within −13% to +5% and standard deviations (rms) of the relative differences are within 3–19% between 25 and 38 km. The rmd and rms with scaled SAGE II NO₂ profiles are in the range of −9 to +7 and 10–17% respectively between 22 and 39 km.     

Interplanetary scintillations of PKS 2314+03 during occultation by comet Halley

Strong interplanetary scintillations (IPS) of the quasar 2314+03 were recorded at 103 MHz at Thaltej-Ahmedabad, India with a transit type correlation interferometer on 18, 19 and 20 December 1985, as the radio source was predicted to be occulted by the ion tail of the comet Halley.

On 18th through 20th very strong scintillations, with periodicities of 1 sec average were observed, their amplitude progressively decreasing as the source approached the tail-end. The rms variations of scintillating flux of the source on 18, 19 & 20 were about 18, 11 & 4.7 Jy, as against 3.3 Jy on control days 17 and 21 December for solar elongation of 87°.

Assuming Gaussian irregularities with weak scattering, the rms density variations, ΔN, of 10, 6, 3 and 1 elec./cm³ on 18 through 21 December, from the comet nucleus towards its tail-end, varied as (ΔN) ∝ r^−3.3 as against (ΔN) ∝ r⁻² in the solar plasma.

Quasi-periodic modulations of the enhanced scintillating flux possibly imply 10⁴ km scale-size ion condensations and mean electron density of 10³ to 10⁴ electrons/cm³ in the Halley's plasma tail.     

Hard X-ray spectral properties and discovery of narrow annihilation line in the spectrum of Nova Muscae

The observations of X-ray Nova in Musca (GRS1124-684) by two coded mask telescopes on board GRANAT observatory provided spectral data in broad 3 – 1300 keV band. During these observations, spanned over a year, the Nova was detected in a three apparently different spectral states, corresponding to different epochs of the soft X-ray light curve: (1) A spectrum with two distinct components (soft, below 8 keV and hard power law tail with slope 2.5, detected up to 300 keV). The soft emission changed gradually with characteristic decay time around 30 days, while power law component exhibited strong variability on the time scales of several hours and decreased much more slowly. (2) A soft spectrum (without hard power law tail), observed during the “kick” of the soft X-ray light curve. (3) A hard power law spectrum with slope 2.2. Thus, while the 3 – 300 keV luminosity decreased by more than order of magnitude, the source passed through all spectral states known for galactic black hole candidates (Cyg X-1, GX339-4, 1E1740.7-2942, GRS1758-258 etc.).

On January 20–21 1991, the SIGMA telescope aboard GRANAT detected a relatively narrow variable emission line near 500 keV (Fig.1,2) with net flux ≈ 6 · 10⁻³ phot/s/cm², most probably related with electron-positron annihilation processes, occurring in the source /1–4/. Additional excess above power law continuum, centered around 200 keV, was found during this observation.     

Models for horizontal E- and F-region drifts

Plasma transport is very important for understanding the space-time variations of the ionosphere. Therefore, following a resolution of URSI Subcommission G4, an effort is made to create a computer code describing the main results of investigations the ionospheric drift which were not considered in IRI-1979.

The experimental data from 23 stations in the Northern Hemisphere were obtained between 1957 and 1970. The worldwide coverage in geographic latitude is 7°N to 71°N (7.5° to 64.1° geomagnetic) and O° to 131°E geographic longitude.

We have developed appropriate procedure which allow us to infer from these data the main parameters of the global ionospheric motions at E- and F-region levels.

An algorithm for computing the zonal and meridional drift components VX, VY can be found in IRI-1990.

The last version of the computer programm called DRIFT which does the test calculation of Ionospheric Drifts Global Model whith printing the tables at the Epson printer is written in Turbo ascal for the IBM PC AT 286/287 compatible computers. Program code (execute module) is about 25 Kbyte. Data files are about 10 Kbyte.

E- and F-region horizontal ionospheric irregularities drift data, worldwide obtained from 1957 to 1970 by D1 and D3 methods, are statistically analysed and a computer code for the average velocity variations in latitude and local time for some solar activity levels is constructed. The PC program DRIFT allows to determine zonal and meridional drift velocities of ionospheric irregularities at the lower (90 < h < = 140 km) and upper (h > 140 km) ionosphere.

The main block of the program DRIFT is the procedure DRIRR for calculating VX and VY for a period (P), geomagnetic (geographic) latitude (FI) and local time (LT) to be specified.

The example of the program DRIFT calculation for F-region (REG=2) and for the whole period of observations (P=1) is in Table. VX > 0 to east, VY > 0 to north. FI is geomagnetic latitude.     

Gamma-telescope with very high angular and spectral resolution

New type of gamma-telescope with angular resolution about several seconds of arc and spectral resolution ΔE/E <0.1% is proposed. In this instrument a position sensitive detector is used together with random mask, crystal diffractor and stellar sensor. The scientific objectives and the possible ways to carry out the first experiment with this telescope are discussed.     

Storm-time formation of a relativistic electron belt and some relevant phenomena in other magnetospheric plasma domains

An empirical formula relating the strength of a storm given by its |Dst|_max with the L-coordinate of the peak of storm-injected relativistic electrons is one of a few well-confirmed quantitative relations found in the magneto-spheric physics. We successively extended a dataset of the formula’s basic storms with several events of high Dst-amplitude up to the highest observed |Dst|_max = 600 nT. Possible applying of the formula to the predicting of the ring-current plasma-pressure distribution and the lowest westward electrojet position for a storm are discussed. We have also analyzed the 2000–2001 years’ data on relativistic electrons from our instruments installed on EXPRESS-A (geosynchronous orbit; E_e = 0.8–6 MeV), Molniya-3 (h = 500 × 40 000 km, i = 63°; E_e = 0.8–5.5 MeV) and GLONASS (h = 20 000 km, i = 64°; E_e  l MeV) along with other correlated measurements: GOES series (E_e > 2 MeV), geomagnetic indices (Dst, AE, AL) and interplanetary parameters (solar wind, IMF). The goal is to investigate which outer conditions are most responsible for the high/low output of the storm-injected relativistic electrons. For the geosynchronous orbit, two factors are found as the necessary condition of the highest electron output: high and long-lasting substorm activity on a storm recovery phase and high velocity of solar wind. On the contrary, extremely low substorm activity surely observed during whole the storm recovery phase constitutes a sufficient condition of the non-increased after-storm electron intensity. For the first time found cases of the increased after-storm electron intensity observed at the inner L-shells with no simultaneously seen increase in the geosynchronous distances are presented.     

A study of the solar cycle signal on total ozone over low-latitude Brazilian observation stations

Observations of total ozone at low latitudes in Brazil have been made using Dobson spectrophotometers since 1974 for Cachoeira Paulista (23.1° S, 45° W) and since 1978 for Natal (5.8° S, 35.2° W). Annual averages, 12 months and 36 months running averages have been analyzed. Spectral analyses of the data revealed that the most important periods found (confidence level> 90%) were: for Natal, 2.5 years (93.1%, quasi-biennial oscillation-QBO) and 10 years (98,2%, possibly the solar cycle signal); for Cachoeira Paulista, 2.4 years (96.8%, QBO) and 8 years (99.6%). The difference in total ozone between maximum and minimum solar cycles were estimated, using yearly averages of total ozone. For solar cycle 21, 1.16% and 1.26% for Natal and Cachoeira Paulista were found; for solar cycle 22, a larger difference of 3.8% for Natal and 4.1% for Cachoeira Paulista were found. The corresponding variation in UV-B at 300 nm, using Beer's law, is 8–10% for C. Paulista and 4–5% for Natal, with maxima occurring during the minimum of the solar cycle.     

Mesospheric nitric oxide and ozone measurements in polar winter at 69°N

Two rocket experiments were carried out just before and after the polar night at Andoya (69°N), Norway to investigate transport of nitric oxide produced by auroral processes into the middle atmosphere and its influence on the ozone chemistry. Nitric oxide densities of (2–5) × 10⁸cm⁻³ found in the 70–90 km region are one to two orders of magnitude larger than those at middle latitudes. The influence on ozone densities in the 70–90 km region due to such enhanced nitric oxide abundance is found to be insignificant as compared to that due to transport in the middle of February. The larger ozone densities found in February (in spite of longer sunlit duration) than in November in the 40–60 km region again support predominance of transport over photochemical loss.     

VEGA three-channel spectrometer experiment: Spectroscopy of comet Halley in the visible and near-ultraviolet ranges

A total of 3600 spectra of Comet Halley in the 275–710 nm were obtained on March, 8, 9, 10 and 11, 1986, from the VEGA 2 spacecraft. The emissions of OH, NH, CN, C₃, CH, C₂, NH₂ and H₂O⁺ are identified. From the OH intensity in the (0,0) band: 1.1 Megarayleigh at 5400 km from the nucleus, it can be inferred that the OH production rate was (1.4 ± 0.5)×10³⁰ molecules s⁻¹. The NH, C₃, CH and NH₂ bands became comparatively more intense at distances from the nucleus shorter than 3000km. At 06:40 U.T. when the instrument field of view was 6000×4500 km, two jets were observed. Spectra from the jets show significant differences with other spectra. Inside a jet NH, C₃ and NH₂ are comparatively more intense and the rotational distributions of OH, CN and C₂ are strongly distorted. This shows that part of the observed emissions probably comes from radicals directly produced in the excited state during the initial process of photolysis of the parent molecules.