Context. The SOLar SPECtrum (SOLSPEC) experiment is part of the Solar Monitoring Observatory (SOLAR) payload, and has been externally mounted on the Columbus module of the International Space Station (ISS) since 2008. SOLAR/SOLSPEC combines three absolutely calibrated double monochromators with concave gratings for measuring the solar spectral irradiance (SSI) from 166 nm to 3088 nm. This physical quantity is a key input for studies of climatology, planetary atmospheres, and solar physics.Aims. A general description of the instrument is given, including in-flight operations and performance of the ultraviolet (UV) channel from 175 nm to 340 nm.Methods. We developed a range of processing and correction methods, which are described in detail. For example, methods for correcting thermal behavior effects, instrument linearity, and especially the accuracy of the wavelength and absolute radiometric scales have been validated by modeling the standard uncertainties.Results. The deliverable is a quiet Sun UV reference solar spectrum as measured by SOLAR/SOLSPEC during the minimum of solar activity prior to cycle 24. Comparisons with other instruments measuring SSI are also presented.

On 7 February 2008, the SOLAR payload was placed onboard the International Space Station. It is composed of three instruments, two spectrometers and a radiometer. The two spectrometers allow us to cover the 16 – 2900 nm spectral range. In this article, we first briefly present the instrumentation, its calibration and its performance in orbit. Second, the solar spectrum measured during the transition between Solar Cycles 23 to 24 at the time of the minimum is shown and compared with other data sets. Its accuracy is estimated as a function of wavelength and the solar atmosphere brightness-temperature is calculated and compared with those derived from two theoretical models.

The Solar Diameter Imager and Surface Mapper (SODISM) on board the PICARD space mission provides wide-field images of the photosphere and chromosphere of the Sun in five narrow pass bands (centered at 215.0, 393.37, 535.7, 607.1, and 782.2 nm). PICARD is a space mission, which was successfully launched on 15 June 2010 into a Sun synchronous dawn-dusk orbit. It represents a European asset aiming at collecting solar observations that can serve to estimate some of the inputs to Earth climate models. The scientific payload consists of the SODISM imager and of two radiometers, SOVAP (SOlar VAriability PICARD) and PREMOS (PREcision MOnitor Sensor), which carry out measurements that allow estimating the Total Solar Irradiance (TSI) and the Solar Spectral Irradiance (SSI) from the middle ultraviolet to the red. The SODISM telescope monitors solar activity continuously. It thus produces images that can also feed SSI reconstruction models. Further, the objectives of SODISM encompass the probing of the interior of the Sun via helioseismic analysis of observations in intensity (on the solar disc and at the limb), and via astrometric investigations at the limb. The latter addresses especially the spectral dependence of the radial limb shape, and the temporal evolution of the solar diameter and asphericity. After a brief review of its original science objectives, this paper presents the detailed design of the SODISM instrument, its expected performance, and the scheme of its flight operations. Some observations with SODISM are presented and discussed.

In this paper, we report the development of low flux short wavelength infrared radio-imaging systems to study the radiance due to nightglow emission. This radiation is mainly due to the desexcitation of hydroxyl molecules in the upper atmosphere. It is present in the visible range and reaches its maximum value (at ground level) in the short wavelength infrared band between 1.4 and 1.8μm. The nightglow may be an interesting additional light source for night vision systems in moonless or cloudy sky conditions. In this paper, we describe the experimental setup and present first results of the measurement campaigns that we performed at the Observatoire de Haute-Provence in France and at the European Southern Observatory site of La Silla in Chile.

SOLAR is a set of three solar instruments measuring the total and spectral absolute irradiance from 16 nm to 3080 nm for solar, atmospheric and climatology physics. It is an external payload for the COLUMBUS laboratory launched on 7 February 2008. The mission’s primary objective is the measurement of the solar irradiance with the highest possible accuracy, and its variability using the following instruments: SOL-ACES (SOLar Auto-Calibrating EUV/UV Spectrophotometers) consists of four grazing incidence planar gratings measuring from 16 nm to 220 nm; SOLSPEC (SOLar SPECtrum) consists of three double gratings spectrometers, covering the range 165 nm to 3080 nm; and SOVIM (SOlar Variability Irradiance Monitor) is combining two types of absolute radiometers and three-channel filter – radiometers. SOLSPEC and SOL-ACES have been calibrated by primary standard radiation sources of the Physikalisch-Technische Bundesanstalt (PTB). Below we describe SOLSPEC, and its performance.

The SOLSPEC, SSBUV, and SUSIM spectrometers simultaneously observed the solar spectral irradiance during the ATLAS-1 mission flown on board the Space Shuttle Atlantis in March 1992. The three instruments use different methods and means of absolute calibration and were each calibrated preflight and postflight. The three data sets are reported from 200 to 350 nm at 1.1 nm resolution. The method of comparing the three independent data sets is discussed. The importance of a common, precise wavelength scale is shown when comparing the data in wavelength regions of strong Fraunhofer lines. The agreement among the solar irradiance measurements is better than +5%. The fact that the calibrations of the three instruments were based on three independent s andards provides confidence that the absolute solar spectral irradiance in the range 200-350 nm is now known with an accuracy better than +5%. The mean ATLAS-1 solar spectrum iscompared with simultaneous solar observations from the UARS SOLSTICE and UARS SUSIM instruments. The two mean solar spectra gree to within +3%.

The upper atmosphere dynamics in the polar cap is mainly driven by ion‐drag momentum sources imposed by the mapping of magnetosphere convection into the thermosphere/ionosphere and by Joule and auroral particle heating. Auroral particles also enhance conductivity particularly in the middle and lower ionosphere. Changes in the magnetospheric energy and momentum sources can significantly modify the wind circulation during geomagnetic storms. To observe these effects, a Michelson interferometer has been installed in Svalbard to measure winds in the thermosphere. Prior to 30 October 2003, cloud cover over Svalbard rendered the conditions unfavorable for optical observation. However, meteorological conditions improved after this date to enable the thermospheric response to the 28 October coronal mass ejection to be made. During quiet geomagnetic conditions measured wind velocities were in good agreement with those predicted by the Horizontal Wind Model (HWM). During disturbed geomagnetic conditions, HWM tended to underestimate the observed velocities. Comparison of the wind observations with a physical model tended to show reasonable agreement during both the strongly driven and recovery phase of the storm. Although the physical model did not always capture the timing of the rapid changes in the wind response in the early phase of the storm, the amplitudes of the fluctuations were in good agreement. After the initial phase the physical model agreed well with both the timing and amplitude of the meridional and zonal wind fluctuations. The meridional wind component was also derived from the EISCAT Svalbard Radar ion velocity and was found to be in close agreement with the optical winds observations.

Two new composite solar irradiance reference spectra extending from 0.1 to 2400 nm are constructed using recent space measurements for two distinct time periods during solar cycle 22. For wavelengths above Lyman α, data were gathered from the instruments placed aboard three space platforms, the ATmospheric Laboratory for Applications and Science (ATLAS), the Upper Atmosphere Research Satellite (UARS) and the EUropean Retrieval Carrier (EURECA). Below Lyman α, data from an instrument flown on rockets are used. The two spectra obtained at the time of ATLAS 1 and 3 missions cover about half of the total solar cycle amplitude as gauged by the Mg II and F10.7 solar indices. The accuracy of the spectra varies from 40% in the X-ray to about 3% in the UV–visible, and near IR ranges. A comparison between the total solar irradiance obtained through integration of the reference spectra and their observed values at the time of the ATLAS missions shows agreements of the order of 1%.

The SOLar SPECtrum (SOLSPEC) and the SOlar SPectrum (SOSP) spectrometers are two twin instruments built to carry out solar spectral irradiance measurements. They are made of three spectrometers dedicated to observations in the ultraviolet, visible and infrared domains. SOLSPEC flew with the ATmospheric Laboratory for Applications and Science (ATLAS) while SOSP flew on the EUropean Retrieval CArrier (EURECA) missions. ATLAS 1 and 2 data being already published, this paper is mostly dedicated to the ATLAS 3 and EURECA data in the IR domain. Comparisons between the ATLAS data sets and the Upper Atmosphere Research Satellite (UARS) results are made. EURECA IR data are shown and compared with previous results. Our best UV, visible and IR spectra are finally merged into a single absolute solar irradiance spectrum covering the 200 to 2400 nm domain.

The PICARD microsatellite mission will provide 3 to 4 years simultaneous measurements of the solar diameter, differential rotation and solar constant to investigate the nature of their relations and variabilities. The 110 kg satellite has a 42 kg payload consisting of 3 instruments: SODISM, which will deliver an absolute measure (better than 4 milliarcsec) of the solar diameter and solar shape, SOVAP, measuring the total solar irradiance, and PREMOS, dedicated to the UV and visible flux in selected wavelength bands. Now in Phase B, PICARD is expected to be launched by 2005. We review the scientific goals linked to the diameter measurement with interest for Earth Climate, Space Weather and Helioseismology, present the payload and instruments' concepts and design, and give a brief overview of the program aspects.

The SOLSPEC instrument measures the absolute solar spectral irradiance from 200 to 2500 nm. The instrument flew in March 1992, March 1993 and November 1994 with the three ATLAS missions during 10 days. SOSP is the spare unit of SOLSPEC. It flew on the EURECA platform from 11 August 1992 to May 1993. SOLSPEC and SOSP are made of three spectrometers and contains several lamps allowing to check in flight, the instrument stability and its wavelength scale.

PICARD is a CNES micro-satellite mission due for flight by the end of 2002, named after the name of a French astronomer who first observed with consistency the solar diameter changes during the Maunder minimum in the 16th century. It consists of two instruments measuring (i) the solar diameter and differential rotation, and (ii) the total solar irradiance. These quantities are fundamental for the understanding of the solar-Terrestrial relations, e.g. the influence of the Sun on the Earth's climate, and of the internal structure of the Sun. The continuous — or nearly continuous — viewing of the Sun from an appropriate orbit, the 5 minutes sampling rate and the very low noise measurements, will allow g-modes detection and precise diameter measurements besides accurately establishing the relationship between irradiance and diameter changes. Providing an absolute measure of the solar diameter to 1 milliarcsecond, PICARD is the first step towards instruments capable of accurate and perennial measurements, for the centuries to come, of the solar-terrestrial influence. The objectives of the mission, instrument capabilities, observing modes and performances are described.

The SOLSPEC investigation has already been flown in orbit for measuring the absolute solar spectral irradiance. The scientific objectives for the ISSA mission are presented and their importance is discussed. The performance of the instrument will be shown using the recent SOLSPEC results. For the ISSA mission, changes have been already undertaken in order to meet the ISSA requirements (interfaces and reliability) and several instrumental improvements for a better science return.

The SOLSPEC instrument has been built to carry out absolute solar spectral irradiance measurements from space. It was first flown in December 1983 on mission STS 9 (Spacelab 1), from August 1992 to June 1993 on board the free-flying EURECA platform with mission STS 46 (deployment) and STS 57 (retrieval), then flown three times more with the ATLAS missions STS 45, 56 and 66. Further applications are foreseen in combination with the International Space Station Alpha (ISSA). SOLSPEC covers a wavelength range from 180 nm to 3000 nm split into three separate spectrometer channels (ultraviolet, visible and infrared) and has been calibrated pre- and post-flight using a black body at the Landessternwarte Heidelberg with temperatures up to 3300 K. In this paper the calibration concept is presented, together with a short instrument description and suggestions for improvements in order that higher black-body temperatures can be reached.

The SOLSPEC, SSBUV, and SUSIM spectrometers simultaneously observed the solar spectral irradiance during the ATLAS‐1 mission flown on board the Space Shuttle Atlantis in March 1992. The three instruments use different methods and means of absolute calibration and were each calibrated preflight and postflight. The three data sets are reported from 200 to 350 nm at 1.1 nm resolution. The method of comparing the three independent data sets is discussed. The importance of a common, precise wavelength scale is shown when comparing the data in wavelength regions of strong Fraunhofer lines. The agreement among the solar irradiance measurements is better than ±5%. The fact that the calibrations of the three instruments were based on three independent standards provides confidence that the absolute solar spectral irradiance in the range 200–350 nm is now known with an accuracy better than ±5%. The mean ATLAS‐1 solar spectrum is compared with simultaneous solar observations from the UARS SOLSTICE and UARS SUSIM instruments. The two mean solar spectra agree to within ±3%.