Balloon-borne Solar Telescope Research Articles

Structure and dynamics of isolated internetwork Ca II H bright points observed by SUNRISE

We aim to improve our picture of the low chromosphere in the quiet-Sun internetwork by investigating the intensity, horizontal velocity, size and lifetime variations of small bright points (BPs; diameter smaller than 0.3 arcsec) observed in the Ca II H 3968 {\AA} passband along with their magnetic field parameters, derived from photospheric magnetograms. Several high-quality time series of disc-centre, quiet-Sun observations from the Sunrise balloon-borne solar telescope, with spatial resolution of around 100 km on the solar surface, have been analysed to study the dynamics of BPs observed in the Ca II H passband and their dependence on the photospheric vector magnetogram signal. Parameters such as horizontal velocity, diameter, intensity and lifetime histograms of the isolated internetwork and magnetic Ca II H BPs were determined. Mean values were found to be 2.2 km/s, 0.2 arcsec (150 km), 1.48 average Ca II H quiet-Sun and 673 sec, respectively. Interestingly, the brightness and the horizontal velocity of BPs are anti-correlated. Large excursions (pulses) in horizontal velocity, up to 15 km/s, are present in the trajectories of most BPs. These could excite kink waves travelling into the chromosphere and possibly the corona, which we estimate to carry an energy flux of 310 W/m^2, sufficient to heat the upper layers, although only marginally. The stable observing conditions of Sunrise and our technique for identifying and tracking BPs have allowed us to determine reliable parameters of these features in the internetwork. Thus we find, e.g., that they are considerably longer lived than previously thought. The large velocities are also reliable, and may excite kink waves. Although these wave are (marginally) energetic enough to heat the quiet corona, we expect a large additional contribution from larger magnetic elements populating the network and partly also the internetwork.

Thermal control of SUNRISE, a balloon-borne solar telescope

SUNRISE is a balloon-borne solar telescope flown with a long-duration balloon by NASA's Columbia Scientific Balloon Facility team from Esrange (Swedish Space Corporation), on 8 June 2009. SUNRISE has been a challenging mission from the thermal point of view because of its size and power dissipation. Thus, a dedicated thermal analysis has been carried out to find a solution that allows all the devices to be kept within their appropriate temperature ranges, without exceeding the allowable temperature gradients, critical for optical devices. In this article, the thermal design of SUNRISE is described. A geometrical mathematical model and a thermal mathematical model of the whole system have been set up for the different load cases in order to obtain the temperature distribution and gradients in the system. Some trade-offs have been necessary to fulfil all the thermal requirements. The thermal hardware used to achieve it is described. Finally, the temperatures obtained with the models have been compared with flight data.

QUIET-SUN INTENSITY CONTRASTS IN THE NEAR-ULTRAVIOLET AS MEASURED FROM SUNRISE

We present high-resolution images of the Sun in the near-ultraviolet spectral range between 214 nm and 397 nm as obtained from the first science flight of the 1 m SUNRISE balloon-borne solar telescope. The quiet-Sun rms intensity contrasts found in this wavelength range are among the highest values ever obtained for quiet-Sun solar surface structures—up to 32.8% at a wavelength of 214 nm. We compare the rms contrasts obtained from the observational data with theoretical intensity contrasts obtained from numerical magnetohydrodynamic simulations. For 388 nm and 312 nm the observations agree well with the numerical simulations whereas at shorter wavelengths discrepancies between observed and simulated contrasts remain.

SUNRISE: High resolution UV/VIS observations of the sun from the stratosphere

SUNRISE is an international project for the development, construction and operation of a balloon-borne solar telescope with an aperture of 1 m, working in the UV/VIS spectral domain. The main scientific goal of SUNRISE is to understand the structure and dynamics of the magnetic field in the atmosphere of the Sun. SUNRISE will provide near diffraction-limited images of the photosphere and chromosphere with an unprecedented resolution down to 35 km on the solar surface at wavelengths around 220 nm. Active in-flight alignment and image stabilization techniques are used. The focal-plane instrumentation consists of a polarization sensitive spectrograph, a Fabry–Perot filter magnetograph and a phase-diverse filter imager working in the near UV. The first stratospheric long-duration balloon flight of SUNRISE is planned in summer 2009 from the Swedish ESRANGE station. SUNRISE is a joint project of the German Max-Planck-Institut für Sonnensystemforschung (MPS), Katlenburg-Lindau, with the Kiepenheuer-Institut für Sonnenphysik (KIS), Freiburg, Germany, the High-Altitude Observatory (HAO), Boulder, USA, the Lockheed-Martin Solar and Astrophysics Laboratory (LMSAL), Palo Alto, USA, and the Spanish IMaX consortium. This paper will give an overview about the mission and a description of its scientific and technological aspects.

High resolution spectro-polarimetry with a large balloon-borne solar telescope

The balloon mission “Sunrise” consists of a 1m lightweight solar telescope equipped with a powerful spectro-graph-polarimeter and a multi-channel filtergraph for the visible and the UV. The science goals of Sunrise are focussed on, but not limited to, the investigation of the solar surface magnetism. The key questions include the generation and maintenance of the variable magnetic field, the structure and dynamics of the chromosphere, and the interaction of material flow and magnetic field in sunspots.

Attitude control and high precision pointing control system of a large balloon borne solar telescope

Abstract In this paper, we have discussed the development of a large Control Moment Gyroscope (51 N.M.S. CMG) and use CMG as the driving component to realize precise attitude control of a large balloon borne gondola (total weight 1.5 ton) on which the solar telescope, 80 cm in diameter, is equatorially mounted. On ground test, the pointing accuracy of the gondola of better than 1 arc-minute (R.M.S.) at its plumb line have finally been achieved. In addition, we have established a control model of the large balloon borne telescope pointing control system. By computer simulation and actual test on ground, we have achieved the pointing accuracy of better than 10 arc-seconds (R.M.S.) for the solar telescope.

Ballon-borne and ground-mobile solar telescope

The balloon-borne and ground-mobile solar telescope is a middle step of the Space Solar Telescope (SST) (Ai, 1995). The system is much similar to the main optical telescope of the SST, but differ with 80cm diameter. The total weight of the telescope and gondola 1500kg, the balloon cube about 200,000M 3, flying altitude 32km. It will be launched twice in May and September, 1997.

Balloon-borne ultraviolet solar telescope and high resolution echelle-spectrograph: Instrumentation and first results

A description of the LPSP balloon-borne telescope — spectrograph combination is given. The payload comprises a one-axis stabilized platform carrying a two-axes equatorial pointing system; the instrumentation directed towards the Sun is a 300 mm telescope coupled with an echelle spectrograph and a slit jaw camera. The scientific objective of the experimental set-up is to observe spatial, spectral, and temporal variations of fine structures of the solar atmosphere, using ballon ultraviolet windows between 190 and 300 nm, with very high angular and spectral resolutions (0.5 arc sec and 1 pm). In the configuration of the first flight which successfully took place on 1 October, 1982 from Aire-sur'l'Adour (Landes), many stigmatic spectra of the Sun were recorded in the 190–213 and 272–293 nm ranges, with an angular resolution of 4 arc sec and a spectral resolution of 1.5 to 2 pm.

Determination of stratospheric H 2O and O 3 column densities from balloon altitude far infrared absorption spectra by a curve of growth method

Pure rotational lines of H 2O, Q branches of O 3 and single lines of O 3 in the far infrared absorption spectrum of the stratosphere, taken at an altitude of 29.1 km above Texas on 19 June, 1978 from a balloon-borne solar telescope equipped with a rapid-scanning Michelson interferometer, have been analyzed by a curve-of-growth method to yield good values of vertical column densities for these important minor constituents. In this mid-latitude atmosphere, vertical column densities of H 2O and O 3 were found to be 1.32(±0.39) × 10 18 and 1.72(±0.55) × 10 18 molecules cm −2, respectively, the major contribution to the uncertainty coming from a correction to the overall spectral envelope necessitated by detector nonlinearity in this specific flight. The present data demonstrate the promise of this technique for the measurement of number density profiles of other important minor constituents, such as HCl, H 2O 2, NO 2, HO 2 which are expected to contribute to this spectrum in the stratosphere.

Guiding System of the Spectro-Stratoscope

The characteristics of the guiding system of the Spectro-Stratoscope (a balloon-borne solar telescope) for spectroscopic studies of the sun are described. The telescope system is almost completely decoupled from the balloon suspension. Hydrostatic bearings and a spherical torque motor are described in detail. The fine-stage guiding system locking on the solar granulation is described and the principle of automatic focusing explained.

Fine structure of brightness, velocity and magnetic field in the penumbra

As a preparation for the observational program of the first flight of the ‘Spectro-Stratoscope’ balloon-borne solar telescope, an attempt was made with the 35-cm aperture domeless Coudé refractor of the Capri Station of Fraunhofer Institute to obtain spectra of penumbral fine structure.