Simulation study for the determination of the lunar gravity field from PRARE-L tracking onboard the German LEO mission

A simulation study has been performed at GFZ Potsdam, which shows the anticipated improvement of the lunar gravity field model with respect to current (LP150Q model) or near-future (SELENE) knowledge in the framework of the planned German Lunar Explorations Orbiter (LEO) mission, based on PRARE-L (Precise Range And Range-rate Equipment – Lunar version) Satellite-to-Satellite (SST) and Satellite-Earth-Satellite (SEST) tracking observations. It is shown that the global mean error of the lunar gravity field can be reduced to less than 0.1 mGal at a spatial resolution of 50 km. In the spectral domain, this means a factor of 10 (long wavelengths) and some 100 (mid to short wavelengths) improvement as compared to predictions for SELENE or a factor of 1000 with respect to LP150Q. Furthermore, a higher spatial resolution of up to 28 km seems feasible and would correspond to a factor of 2–3 improvement of SELENE results. Moreover, PRARE-L is expected to derive the low-degree coefficients of the lunar gravity field with unprecedented accuracy. Considering long mission duration (at least 1 year is planned) this would allow for the first time a precise direct determination of the low-degree tidal Love numbers of the Moon and, in combination with high precision SEST, would provide an experimental basis to study relativistic effects such as the periselenium advance in the Earth–Moon system.     

High resolution science with high redshift galaxies

We summarize the high-resolution science that has been done on high redshift galaxies with Adaptive Optics (AO) on the world’s largest ground-based facilities and with the Hubble Space Telescope (HST). These facilities complement each other. Ground-based AO provides better light gathering power and in principle better resolution than HST, giving it the edge in high spatial resolution imaging and high resolution spectroscopy. HST produces higher quality, more stable PSF’s over larger field-of-views in a much darker sky-background than ground-based AO, and yields deeper wide-field images and low-resolution spectra than the ground. Faint galaxies have steadily decreasing sizes at fainter fluxes and higher redshifts, reflecting the hierarchical formation of galaxies over cosmic time. HST has imaged this process in great structural detail to z  6, and ground-based AO and spectroscopy has provided measurements of their masses and other physical properties with cosmic time. Last, we review how the 6.5 m James Webb Space Telescope (JWST) will measure First Light, reionization, and galaxy assembly in the near–mid-IR after 2013.     

Studying the evolution of the hot universe with the X-ray evolving universe spectroscopy mission – XEUS

Europe is one of the major partners building the International Space Station (ISS) and European industry, together with ESA, is responsible for many station components including the Columbus Orbital Facility, the Automated Transport Vehicle, two connecting modules and the European Robotic Arm. Together with this impressive list of contributions there is a strong desire within the ESA Member States to benefit from this investment by utilizing the unique capabilities of the ISS to perform world-class science. XEUS is one of the astronomical applications being studied by ESA to utilize the capabilities of the ISS. XEUS will be a long-term X-ray observatory with an initial mirror area of 6 m² at 1 keV that will be expanded to 30 m² following a visit to the ISS. The 1 keV spatial resolution is expected to be 2–5″ half-energy-width. XEUS will consist of separate detector and mirror spacecraft (MSC) aligned by active control to provide a focal length of 50 m. A new detector spacecraft, complete with the next generation of instruments, will also be added after visiting the ISS. The limiting 0.1–2.5 keV sensitivity will then be 4 × 10⁻¹⁸ erg cm⁻² s⁻¹, around 200 times better than XMM-Newton, allowing XEUS to study the properties of the hot baryons and dark matter at high redshift.     

HIRDES – The High-Resolution Double-Echelle Spectrograph for the World Space Observatory Ultraviolet (WSO/UV)

The World Space Observatory Ultraviolet (WSO/UV) is a multi-national project grown out of the needs of the astronomical community to have future access to the UV range. WSO/UV consists of a single UV telescope with a primary mirror of 1.7 m diameter feeding the UV spectrometer and UV imagers. The spectrometer comprises three different spectrographs, two high-resolution echelle spectrographs (the High-Resolution Double-Echelle Spectrograph, HIRDES) and a low-dispersion long-slit instrument. Within HIRDES the 102–310 nm spectral band is split to feed two echelle spectrographs covering the UV range 174–310 nm and the vacuum-UV range 102–176 nm with high spectral resolution (R > 50,000). The technical concept is based on the heritage of two previous ORFEUS SPAS missions. The phase-B1 development activities are described in this paper considering performance aspects, design drivers, related trade-offs (mechanical concepts, material selection etc.) and a critical functional and environmental test verification approach. The current state of other WSO/UV scientific instruments (imagers) is also described.     

Fast spectroscopy of the 4 November 1978 gamma-ray burst

The Franco-Soviet Signe experiments on Venera 11 and Venera 12 allow a spectral analysis of gamma-ray bursts with a time resolution of 250 ms. Evidence is presented for i) short annihilation flashes of up to 20 photons cm⁻²s⁻¹ and ii) rapid variations of the continuum, from a study of the intense 4 November 1978 event.     

Dark matter search with the CALET detector on-board ISS

The CALorimetric Electron Telescope, CALET, mission is proposed for the observation of high-energy electrons and gamma-rays at the Exposed Facility of the Japanese Experiment Module on the International Space Station. The CALET has a capability to observe the electrons (without separation between e⁺ and e⁻) in 1 GeV–10 TeV and the gamma-rays in 20 MeV–several TeV with a high-energy resolution of 2% at 100 GeV, a good angular resolution of 0.06 degree at 100 GeV, and a high proton-rejection power of nearly 10⁶. The CALET has a geometrical factor of 1 m²sr, and the observation period is expected for more than three years. The very precise measurement of electrons enables us to detect a distinctive feature in the energy spectrum caused from WIMP dark matter in the Galactic halo. The excellent energy resolution of CALET, which is much better than GLAST or air Cherenkov telescopes over 10 GeV, enables us to detect gamma-ray lines in the sub-TeV region from WIMP dark matter annihilations. The CALET has, therefore, a unique capability to search for WIMP dark matter by the hybrid observations of electrons and gamma-rays.     

A proportional counter/image intensifier system for the detection of low energy X-rays

Proportional counters (PC's) and gas scintillation proportional counters (GSPC's) currently used for detection of low energy X-rays provide information on event position and energy. Although at 1.5 keV PC's have good position resolution (～ 200 μm FWHM) they have relatively poor energy resolution (～ 40% FWHM). Conversely GSPC's have reasonable energy resolution (～ 20% FWHM), but poor spatial resolution (～ 1mm FWHM).We describe a scheme in which a parallel plate PC with a transparent anode deposited on a fibre optic substrate has been used. This allows the light emitted by electron avalanches caused by X-ray events in the PC to be detected by an image intensifier with electronic readout. Using this scheme spatial resolution better than that of conventional PC's should be attainable. In addition avalanches induced by single electrons can be resolved through observation of the time structure of the light flash. Using the ability to count the number of primary electrons created by each X-ray event, it is shown that energy resolution can be achieved which is comparable to that of the GSPC.     

Statistical characterisation of spread F over South Africa

The occurrence of mid-latitude spread F (SF) over South Africa has not been extensively studied since the installation of the DPS-4 digisondes in 1996 and 2000 at Grahamstown (33.32 °S, 26.50 °E) and Madimbo (22.38 °S, 30.88 °E) respectively. This study is intended to quantify the probability of occurrence of F region disturbances associated with SF over South Africa. A study was conducted using data for 8 years (2001–2008) over Madimbo (with a time resolution of 30 min) and Grahamstown (with a variable time resolution of 15 and 30 min). In this study, SF has been classified into frequency SF (FSF), range SF (RSF) and mixed SF (MSF). The SF events were identified by manually identifying ionograms showing SF and tabulating them according to type for further statistical analysis. The results show that the diurnal pattern of SF peaks strongly between 01:00 and 02:00 local time, LT (LT = UT + 2 h), where UT is the universal time. This pattern is true for all seasons and types of SF at Madimbo and Grahamstown in 2001 and 2005, except for RSF which had peaks during autumn and spring in 2001 at Madimbo. The probability of both MSF and FSF tends to increase with decreasing solar activity, with a peak in 2005 (a moderate solar activity period). The seasonal peaks of MSF and FSF are more frequent during winter months at both Madimbo and Grahamstown. In this study, SF was evident in ∼0.03% and ∼0.06% of the available ionograms at Madimbo and Grahamstown respectively during the 8 years.     

Experimental study of morphological and convective instabilities: The MEPHISTO space program

It is now well established that the morphological instability, i.e. the transition during solidification from a planar L/S interface to a cellular one, is strongly influenced by convection. The most recent theories on this topic, which are very advanced, suffer from the lack of experimental tests because uncontrolled convective effects cannot be avoid on the ground. Moreover the check of all the pertinent solidification parameters are not controlled in the same time or measured in real time. After a review of the main 1g experiments and their own limitations, we describe a new apparatus (MEPHISTO) which allows :

• •in-situ measurements of the main solidification parameters and in particular the undercooling at the solidification front in real time by a non perturbative method.
• •real time supervision of convective motions influence on crystal growth. First results obtained under 1g condition are presented :
  • ◦hydrodynamic scaling laws testing,
  • ◦instabilities detection,
  • ◦transient phenomena.

Main space results are then anticipated including the role of g-jitters.     

Solar maximum mission experiment: Ultraviolet spectroscopy and polarimetry on the solar maximum mission

We describe the Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission (SMM) spacecraft. The instrument, which operates in the wavelength range 1150 – 3600 Å, has a spatial resolution of 2–3 arc sec and a spectral resolution of 0.02 Å FWHM in second order. A Gregorian telescope, focal length 1.8 m, feeds a 1 m Ebert-Fastie spectrometer. A polarimeter comprising rotating Mg F₂ waveplates can be inserted behind the spectrometer entrance slit and allows all four Stokes parameters to be determined. The observing modes include rasters, spectral scans, velocity measurements, and polarimetry. Finally, we present examples of initial observations made since launch.     

Preliminary results of a meteorological payload being developed by IITM

A meteorological rocket payload developed at the Indian Institute of Tropical Meteorology (IITM) using thermistor as a temperature sensor was flight tested on RH-200 rocket at Thumba (08° 32'N, 76° 52'E), India, during February/April 1982 on four occasions. The corrected data obtained with this payload are compared with Russian rocket, M-100, data. The temperature profile obtained with IITM payload is warmer above 45-km, as compared with M-100 temperature profile, on all occasions. Meridional and zonal winds also agree up to 45-km level. Temperature records show a wave pattern varying in amplitude and frequency in the 20 to 45-km range.     

A neutral gas mass spectrometer to measure the chemical composition of the stratosphere

The Polar Balloon Atmospheric Composition Experiment (P-BACE) is a new generation of neutral gas mass spectrometer based on the time-of-flight principle. P-BACE is the scientific experiment on the Mars Environment Analog Platform (MEAP) flown successfully on a balloon mission in summer 2008. The MEAP mission was flown with a 334,000 m³ helium balloon in the stratosphere on a semicircular trajectory from northern Sweden around the North Pole to Canada using the summer northern hemispheric wind current. The atmospheric conditions at an atmospheric altitude of 35–40 km are remarkably similar to those on the surface of Mars and thus the balloon mission was an ideal testbed for our mass spectrometer P-BACE. Originally this instrument was designed for in situ measurements of the chemical composition of the Martian atmosphere.P-BACE has a unique mass range from 0 to 1000 amu/q with a mass resolution m/Δm (FWHM) > 1000, and the dynamic range is at least six orders of magnitude. During this experiment, the acquisition of one mass spectrum is a sum of 65,535 single spectra, recorded in a time frame of 66 s.The balloon mission lasted 5 days and had successfully demonstrated the functionality of the P-BACE instrument during flight conditions. We had recorded more than 4500 mass spectra. With little modifications, P-BACE can be used on a planetary mission for Mars, but for example also for Venus or Mercury, if placed on a satellite.     

Ultraviolet spectroscopy of the chromosphere and transition zone at high spatial and temporal resolution

The third rocket flight of the NRL High Resolution Telescope and Spectrograph (HRTS) recorded UV spectra of the quiet Sun in a 10″ × 800″ region. By rastering the slit in 2′' increments, a time series with 20s resolution of two-dimensional spectra with 1′' spatial resolution was obtained. The spectrum includes strong chromospheric diagnostic lines of C I, Si I, and Fe II, transition zone lines of C IV and the continuum which is produced in the temperature minimum. Images of the network show that Fe II emission is well-correlated with dark Hα mottles, that the transition zone is produced in extended structures which are apparently continuations of the mottles, and that the strongest continuum emission is from near the base of the mottles. Time series of C I profiles show little variation in most features aside from the chromospheric jets which develop rapidly over timescales of 30s. The C IV profiles also show only gradual variations over most of the slit except for the numerous small explosive events.     

Investigations of artificial HF plasma turbulence features using stimulated electromagnetic emission

New results on growth and decay times of the stimulated electromagnetic emission (SEE), obtained using a special quasi-continuous schedule of HF pump wave radiation, are presented. The employed technique allows to study the evolution of HF plasma turbulence with a high time resolution ( 0.25 ms). It is established that for the broad continuum SEE component the emission intensity starts to decrease within the delay time τ_D 0.5−3.2 ms after pump wave turn-off, where longer times correspond to lower SEE frequencies. The effect is explained in terms of transfer of HF-excited plasma waves throughout their spectrum due to induced scattering by thermal ions.     

Gamma-ray burst detection capabilities of comptel

The imaging gamma-ray telescope COMPTEL, capable of detecting gamma rays in the 1 to 30 MeV range, is one of four experiments onboard NASA's Gamma-Ray Observatory GRO. Besides its primary objectives COMPTEL will contribute to the understanding of cosmic gamma-ray bursts. Summarising, COMPTEL localises bursts (S (E > 1 MeV) ≥ 2.10⁻⁶ erg/cm²) within 1 sr FOV to better than 1° at medium gamma-ray energies, measures continuum energy spectra in the range 0.1 MeV to 20 MeV with fluence S ≥ 6.9 10⁻⁷ erg/cm² (5σ, E≥100 keV), measures gamma-ray lines with detector resolution 9.6% (at 0.5 MeV) and 7.0% (at 1.5 MeV) and determines time histories of both gamma-ray line and continuum emission with t ≥ 0.1 sec resolution.     

Technology challenges for space interferometry: The option of mid-infrared integrated optics

Nulling interferometry is a technique providing high angular resolution which is the core of the space missions Darwin and TPF. The first objective is to reach a deep degree of starlight cancelation in the range 6–20 μm, in order to observe and to characterize the signal from an earth-like planet. Among the numerous technological challenges involved in these missions, the question of the beam combination and wavefront filtering has an important place. A single-mode integrated optics (IO) beam combiner could support both the functions of filtering and the interferometric combination, simplifying the instrumental design. Such a perspective has been explored in this work within the project Integrated Optics for Darwin (IODA), which aims at developing a first IO combiner in the mid-infrared. The solutions reviewed here to manufacture the combiner here are based on infrared dielectric materials on one side, and on metallic conductive waveguides on the other side. With this work, additional inputs are offered to pursue the investigation on mid-infrared photonics devices.     

A comparison of different regression models for downscaling Landsat and MODIS land surface temperature images over heterogeneous landscape

Remotely sensed high spatial resolution thermal images are required for various applications in natural resource management. At present, availability of high spatial resolution (<200 m) thermal images are limited. The temporal resolution of such images is also low. Whereas, coarser spatial resolution (∼1000 m) thermal images with high revisiting capability (∼1 day) are freely available. To bridge this gap, present study attempts to downscale coarser spatial resolution thermal image to finer spatial resolution using relationships between land surface temperature (LST) and vegetation indices over a heterogeneous landscape of India. Five regression based models namely (i) Disaggregation of Radiometric Temperature (DisTrad), (ii) Temperature Sharpening (TsHARP), (iii) TsHARP with local variant, (iv) Least median square regression downscaling (LMS_DS) and (v) Pace regression downscaling (PR_DS) are applied to downscale LST of Landsat Thematic Mapper (TM) and Terra MODIS (Moderate Resolution Imaging Spectroradiometer) images. All the five models are first evaluated on Landsat image aggregated to 960 m resolution and downscaled to 480 m and 240 m resolution. The downscale accuracy is achieved using LMS_DS and PR_DS models at 240 m resolution at 0.61 °C and 0.75 °C respectively. MODIS data downscaled from 1000 m to 250 m spatial resolution results root mean square error (RMSE) of 1.43 °C and 1.62 °C for LMS_DS and PR_DS models, respectively. The LMS_DS model is less sensitive to outliers in heterogeneous landscape and provides higher accuracy when compared to other models. Downscaling model is found to be suitable for agricultural and vegetated landscapes up to a spatial resolution of 250 m but not applicable to water bodies, dry river bed sand sandy open areas.     

Near real-time estimation of tropospheric water vapour content from ground based GNSS data and its potential contribution to weather now-casting in Austria

The importance of high resolution meteorological analysis of the atmosphere increased over the past years. A detailed analysis of the humidity field is an important precondition for a better monitoring of local and regional extreme precipitation events and for forecasts with improved spatial resolution. For this reason, the Austrian Meteorological Agency (ZAMG) is operating the spatial and temporal high resolution INCA system (Integrated Now-casting through Comprehensive Analysis) since begin of 2005. Errors in this analysis occur mainly in the areas of rapidly changing and hard to predict weather conditions or rugged topography with extreme differences in height such as the alpine area of Austria. The aim of this work is to provide GNSS based measurements of the tropospheric water vapour content with a temporal resolution of 1 h and a temporal delay of less than 1 h to assimilate these estimates into the INCA system. Additional requirement is an accuracy of better than 1 mm of the precipitable water (PW) estimates.