Advances in infrared and sub-millimeter filters

Infrared filters use a large variety of physical principles and techniques, as can be expected since they cover three decades of the IR spectrum (1 μm - 1 mm). The multilayer interference filters, derived from optical techniques, play the main role in the region 1 μm–40 μm. They have been successfully used in space applications. On the other side of the spectrum is the domain of metallic mesh filters, which is still developing. Bulk absorption, Reststrahlen bands, diffusion and gratings are also used to achieve the desired properties. A short review of this situation is given, with emphasis on the present trends and developments.Infrared and sub-millimeter filters use a large variety of physical principles and techniques that we may classify in two large families.     

The microlesion concept in HZE particle dosimetry.

High energy, high-Z (HZE) particles are present in high-altitude and high-inclination satellite orbits. Most of the HZE dose above LET = 200 keV/micrometer is due to Fe nuclei. Individual HZE particles can damage several cells adjacent to one another along the particle track in tissue. The outcome has been described as a "microlesion" by D. Grahn. The present study attempts to define conditions for microlesions in specific tissues, to seek biological evidence that microlesions are produced, and to evaluate the microlesion as a potentially useful unit of dose in assessing hazards to spaceworkers. Microlesions in individuals cells and hair follicles have been described. Microbial studies have provided some evidence for independent secondary electron action. Whether or not a few hundred microlesions would be damaging to the whole organism depends upon the nature of damage to critical tissues. For example, cancer may occur if microlesions kill several cells in a straight line and mutate other cells alongside the particle track. Fe particle irradiation of the mouse Harderian gland (Fry et al., this issue) produces tumors efficiently. Microlesions in the lens, cornea, and retina need to be considered. Further dialogue is required before a final decision can be made concerning the most appropriate way to assess the HZE hazard.     

V.L.A. observations of flare build-up in coronal loops

Very Large Array (V.L.A.) measurements at 20 cm wavelength map emission from coronal loops with second-of-arc angular resolution at time intervals as short as 3.3 seconds. The total intensity of the 20 cm emission describes the evolution and structure of the hot plasma that is detected by satellite X-ray observations of coronal loops. The circular polarization of the 20 cm emission describes the evolution, strength and structure of the coronal magnetic field. Preburst heating and magnetic changes that precede burst emission on time scales of between 1 and 30 minutes are discussed. Simultaneous 20 cm and soft X-ray observations indicate an electron temperature $\text{T}{}_{\mathrm{e}}\textcolor{red}{}\text{2.5 × 10}{}^7\text{K}$ and electron density $\text{N}{}_{\mathrm{e}}\textcolor{red}{}\text{10}{}^{10}\text{cm}{}^{\mathrm{?3}}$ during preburst heating in a coronal loop that was also associated with twisting of the entire loop in space. We also discuss the successive triggering of bursts from adjacent coronal loops; highly polarized emission from the legs of loops with large intensity changes over a 32 MHz change in observing frequency; and apparent motions of hot plasma within coronal loops at velocities V > 2,000 kilometerspersecond.     

Growth and development of plants flown on the STS-3 Space Shuttle mission

Pre-germinated pine seedlings and germinating oat and mung bean seeds were flown on the STS-3 Space Shuttle mission. Overall, the seedlings grew and developed well in space. Some oat and mung bean roots, however, grew upward. Lignin content was slightly lower in flight tissues and protein content was higher.     

Subjective vertical before and after space flight

Three scientist astronauts on the D1 spacelab mission participated in a series of orientation experiments before and after exposure to orbital weightlessness. Each subject was tilted about a roll axis at 15 deg intervals up to +/-90 deg. At each angle the subject set a luminous line to what he perceived to be the vertical. The results of these tests are presented.     

Research on comets from space

Review of spectrometric and photometric measurements of recent comets from rockets and satellites.     

What you thought you knew about motion sickness isn't necessarily so

Motion sickness symptoms, stimuli, and drug therapy are discussed. Autogenic feedback training (AFT) methods of preventing motion sickness are explained. Research with AFT indicates that participants who had AFT could withstand longer periods of Coriolis acceleration, participants with high or low susceptibility to motion sickness could control their symptoms with AFT, AFT for Coriolis acceleration is transferable to other motion sickness stimuli, and most people can learn AFT, though with varying rates of learning.     

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).     

Prospects for space stellar astrometry

Astrometry is the major astronomical technique to measure distances, masses and motions of stars. Dividing astrometric techniques into five types according to the size of the field in which a single instrument can produce measurements, the present achievements of the Earth-based astrometry are described. The astrometric activities such as measurements of star diameters, double star relative positioning or stellar parallaxes, search for invisible companions, photographic plate reduction, visual and photoelectric meridian and astrolable astrometry are reviewed. Then, the methods used to construct a quasi-inertial celestial reference frame and to materialize it by a fundamental catalogue are presented and discussed. A much better definition of an absolute reference frame is made possible by VLBI, but the problem of extending it to stellar positions is not yet satisfactorily resolved.The limitations of the ground based astrometry are: the atmospheric turbulence and refraction, Earth's motions and the impossibility to view the entire sky with a single instrument. These limitations are discussed and it is shown how astrometry from space can overcome them. A priori, a gain of two orders of magnitudes in accuracy for all types of astrometry is expected, but at this new level of precision, new effects and limitations will appear, as already shown in the studies of the approved programs.Then, the ESA astrometric satellite HIPPARCOS presently under development is presented. The satellite and the payload are described as well as the observing procedures. Several limitations, specific to space borne instrumentation and to the milliarc second accuracy expected have been identified. However the main limitation in precision remains the photon noise. The data reduction methods are sketched. The data downlinked at a rate of 20 kilobits per second have to be used with an equal weight all over the 21/2 years of observation. They are expected to yield a mean accuracy of 2 milliarc seconds in position and parallax and 2 m.a.s. per year in proper motion for most of the 100000 stars of the program (M _b < 9). Stars to be observed by HIPPARCOS have to be carefully selected. The main fields in which the results of HIPPARCOS will be used are listed from the proposals made by the scientific community. The task of constructing the HIPPARCOS input catalogue from these proposals is presented.Another feature of the ESA astrometric satellite is the use of the HIPPARCOS star-mapper as a photometric and position survey of the sky. This experiment, called TYCHO, should give at least 400000 star positions with accuracies of the order of 0.03 to 0.15 depending upon the magnitudes. Two colour instantaneous magnitudes should also be obtained to 0.1–0.4 mag. precision.Several Space-Telescope on-board instruments are also capable to make small field astrometric observations. Accurate imaging is possible with the Wide Field and the Faint Object cameras. Lunar occultations will be performed with the High Speed photometer. But the main astrometric mode of the Space Telescope will be the use of the Fine Guidance Sensors to measure the relative positions of stars to ±0.002. It is described together with its main scientific applications.The establishment of an absolute reference frame is subsequently discussed. Plans using simultaneously VLBI, HIPPARCOS, and Space Telescope observations are described. They consist in linking the HIPPARCOS stellar system to quasars via radio-stars or stars in the vicinity of optical quasars.Finally, several space astrometry proposals are described: long focus space astrometry and two versions of space interferometry.     

GPS Aided Inertial Navigation

The Global Positioning System is an extremely accurate satellite-based navigation system which, after its completion in 1989, will provide users worldwide, 24 hour. all weather coverage. A joint research project among Boeing, Rockwell-Collins, and Northrop has been completed in which a GPS receiver was integrated with a low-cost strap-down inertial navigation system and a flight computer. A Kalman filter in the latter allows in-fight alignment and calibration of the INS. In addition, feedback from the INS to the GPS receiver improves the system's ability to reacquire satellite signals after outages. The resulting system combines the accuracy of GPS with the jamming immunity and autonomy of inertial navigation. System tests were conducted in which a Boeing owned T-33 jet aircraft was flown through known test pattern to align and calibrate the INS. Earlier tests, including tests against an airborne jammer, were conducted in a modified passenger bus.