Search

The Infrared Space Observatory (ISO) will be the first true infrared astronomical observatory in space, operating at wavelengths from 2.5 to 200 micrometers . Launched into a 24 hour orbit, the observatory will be capable of pointing on specific targets for up to ten hours at a time to make observations with a versatile range of instruments including a camera, a photometer, a complement of spectrophotometers and spectrometers with resolving powers ranging up to 20,000 and polarimetric capabilities over a wide spectral range. During its active lifetime of eighteen months, ISO will be used to observe all classes of astronomical phenomena, including solar system objects, stars, the interstellar medium, and galaxies of all kinds out to extreme distances.

The Infrared Space Observatory (ISO) is a European Space Agency (ESA) mission to be launched in the early 1990’s. It will be able to carry out astronomical observations at wavelengths ranging from 3 µm to 200 µm. A complement of instruments permitting imaging photometry, spectrophotometry, spectrophotometric polarimetry as well as spectrometry both at high and at low resolving power, should provide an observer a wide variety of options for the study of chemical species and chemical processes. Proposals to carry out observations with this instrument will be solicited from the astronomical community in ESA member states, and from U.S.astronomers through the National Aeronautics and Space Administration (NASA). No decision has yet been made on wider solicitation.

The Submillimeter Wave Astronomy Satellite (SWAS) was selected for development and flight by NASA in 1989 as one of the initial payloads in the Small Explorer program. SWAS is designed to carry out submillimeter astronomical observations of spectral lines from space. Spectral lines of H/sub 2/, O/sub 2/, /sup 13/CO, and atomic carbon, which are extremely difficult to observe from the ground but which are potentially important tracers of the structure of dense clouds in the interstellar medium, will be simultaneously observed with high spectral resolution. Incoming radiation will be collected by a 55-cm*71-cm offset Cassegrain antenna, with an aggregate surface error >

This has been an exciting meeting in which we saw all the different instruments on ISO revealing strikingly novel results that challenged conventional perceptions with unexpected findings or confirmed long-held astrophysical views which previously had to be taken on faith.

On 4 July 2005 at 1:52 UT the Deep Impact mission successfully completed its goal to hit the nucleus of 9P/Tempel 1 with an impactor, forming a crater on the nucleus and ejecting material into the coma of the comet. The 370 kg impactor collided with the sunlit side of the nucleus with a relative velocity of 10.2 km/s. NASA's Submillimeter Wave Astronomy Satellite (SWAS) observed the 1(10)-1(01) ortho-water ground-state rotational transition in comet 9P/Tempel 1 before, during, and after the impact. No excess emission from the impact was detected by SWAS. However, the water production rate of the comet showed large natural variations of more than a factor of three during the weeks before the impact., to appear in the proceedings of the IAU Symposium No. 231: "Astrochemistry - Recent Successes and Current Callenges". Typo corrected in author affiliation list

For the values of the outflow velocities vinner and radius Rinner that we adopted at the inner edge of the outflows, and vf , the final velocities we cited for large radial distances from the stars, this requires revision of the calculated stellar masses. The corrected masses for NML Cyg and VY CMa become MNML 53 M and MVY 27 M , respectively. If we assume parabolic outflow, instead of FWHM velocities, the terminal velocities vf can be taken to be 26 and 20 km s , respectively, instead of 19 and 17 km s , and the corresponding stellar masses become MNML 41 M and MVY 22 M . Neither the calculated mass-loss rates that we cite in our paper, ṀNMLk 2:4 ; 10 4 M yr 1 and ṀVYk 3:3 ; 10 4 M yr , nor any other aspects or conclusions of the paper are affected by this correction.

Space missions currently on the drawing boards are expected to gather data at rates exceeding the transmission capabilities of today's telemetry systems by many orders of magnitude. Even on current missions, onboard data compression techniques are being implemented to compensate for lack of transmission speed. But while data compression can minimize the loss of data, it is no substitute for transmitting all of the data through a faster communications link. The transmission problem will soon reach crisis proportions and will affect astronomical, Earth resources, geophysical, meteorological, planetary and other space science missions. To overcome this communications bottleneck, the authors advocate the implementation of telemetry systems based on near-infrared laser transmission techniques. The fiber-optics communications industry has developed most of the basic components required for signal transmission in this wavelength band, which should make such a system affordable on scales relevant to the cost of anticipated space science missions.

Within the past year, historians have joined military lobbyists, politicians, reporters, columnists, and editorial writers in literally critiquing to death an exhibition that they never saw, and one that, through their combined efforts, will never take place: the National Air and Space Museum's "The Last Act: The Atomic Bomb and the End of World War II. "' Concentrating solely on the written word and Xerox copies of photographs whose relative sizes in the planned display they did not know, they drew conclusions about an exhibition medium whose main impact derives, not from words on labels, but from an apt juxtaposition of objects, documents, film, sound, and lighting.2 Nor was the text they analyzed a final script, but rather the first of many drafts that would normally follow-and that did, in fact, follow. Immersed in this analysis, they never seemed to notice that, in the midst of the words, phrases, and paragraphs, sat a fifty-six-foot-long, highly polished

It is shown that the universe may consist of a patchwork of domains with different Riemann curvature constants k = 0, +/-1. Features of a phase transition in which flat space breaks up in a transition 2k0 - k(-) + k(+) with initial scale factors R(-) = R(+) are postulated and explored. It is shown that such a transition is energetically permitted, has the equivalent of a Curie temperature, and can lead in a natural way to the formation of voids and galaxies. It is predicted that, if the ambient universe on average is well fitted by a purely k(-) space, with only occasional domains of k(+) containing galaxies, a density parameter of (A(z sub c + 1)) super -1 should be expected, where z sub c represents the redshift of the earliest objects to have condensed, and A takes on values ranging from about 5 to 3. Present observations of quasars would suggest a density of about 0.03 or 0.05, respectively, but it could be lower if earlier condensation took place.

An upper limit is determined for the difference in the deflection of beams of orthogonally polarised radiation passing through the Sun's gravitational field. A null result is anticipated by present theories of gravitation but this prediction has never been tested.

Twenty‐five years ago when I was a graduate student in physics, I was drafted into the Army and sent to Eniwetok in the Marshall Islands. There was plenty of spare reading time for an army private on this tiny atoll, and I had taken along a paperback copy of Fred Hoyle's Frontiers of Astronomy. Hoyle made astronomy exciting and I began to wonder whether I might find a way to enter the field.

We have attempted to detect linear polarization in carbon and hydrogen 76α radio recombination lines from the Hii region NGC 2024. The upper limits set by these measurements are briefly discussed.

Attention is given to the results of a study of radiative cooling in the interstellar clouds of the Orion Nebula through the emission of far-IR and submillimeter radiation. That the gas is 'clumpy' in the ionized region of the nebula is indicated by the far-IR observations of doubly ionized oxygen. With respect to the edges of the ionized region, the excitation temperature for the 3P1 state is 228 K and the observed emission can be plausibly associated with either ionization or shock fronts at the interface between the ionized and neutral region. Consideration is also given to the possibility of an ionized carbon halo, the turbulent state of the molecular cloud, and the need for further laboratory and theoretical analyses.

Comparisons of Saturn observations at far-IR and submillimeter wavelengths, obtained during the earth's March 1980 passage through the plane of Saturn's rings, with spectroscopic observations obtained at an earlier time when the ring plane tilt angle was 21.8 deg, allow a separation of disk and ring contributions to the flux observed in this wavelength range. It is noted that the observed disk emission at 60-180 microns corresponds to a brightness temperature of 104 + or 2 K, and that the brightness temperature of the rings drops 20 K in the 60-80 micron range. An improved estimate of total Saturnian surface brightness is derived which corresponds to an effective temperature of 96.1 + or - 1.6 K.

The thermal fluctuations in radiation are described by the Einstein-Fowler relation $〈{(\ensuremath{\Delta}E)}^{2}〉=k{T}^{2}(\frac{\ensuremath{\partial}〈E〉}{\ensuremath{\partial}T})$. Two terms contribute to this fluctuation, a photon shot noise term and an expression predicted by wave theory. In the present experiment the second term has been measured.

Two schemes are presented in which matter is moved closer to Mars so as to increase the equinoctal precession period of Mars. In such a way the Martian springs, during which Mars is habitable in the long winter model of Sagan (1971) , could be extended and, in fact, prolonged indefinitely. The schemes involve using solar energy to move the satellite Phobos and/or material from the asteroid belt. Difficulties exist with the proposals but they are presented to stimulate discussion.

The total intensity of light scattered by interplanetary dust has usually been directly related to the dust mass lost because of the Poynting-Robertson effect. The scattered light intensity thus would appear to define a dust supply rate that must be maintained if the dust intensity is to remain constant. This work suggests that comets apparently cannot supply this quantity of dust to the cloud, because radiative pressures prevent most of the comet debris and its secondary collision fragments from entering closed orbits about the sun. More observations on the actual emission rates of very-short-period comets may be needed before this can be conclusively established. It is shown that asteroidal collisions can provide sufficient debris, but the injection rate is extremely variable because most of the debris must be produced in very rare collisions between the largest asteroids. It is concluded that no current theory is capable of accounting for a steady cloud. A possible solution might be found in processes that would counter the Poynting-Robertson drag and permit grains to be long lived. The present comet dust supply rate might then be adequate to account for a stationary cloud. An alternative is a highly variable cloud, with dust produced in asteroidal collisions. The present epoch would then have to be one of unusually high dust density.

WE report new diffuse background measurements of the night sky obtained with three submillimetre detectors. These observations were made on December 2, 1970. A liquid-helium cooled telescope was carried by an Aerobee 170 to an altitude of 190 km. Six detectors covering bandwidths in the 5 µm–1.5 mm range were flown: the results from the near infrared detectors will be reported separately.

It has been suggested that a permafrost layer may exist beneath the surface of the Moon. If such a layer were present, H 2 O molecules would be outgassing from the lunar surface. These molecules could be detected by observations of fluorescent radiation from OH radicals produced from the H 2 O by radiative dissociation. It is shown that an outgassing rate from such a lunar permafrost layer as low as 3 × 10 7 molecules / cm 2 - sec could be detected from the surface of the Earth.

Measurements of astronomical background radiation are interesting because when they succeed they tell us the energy budget of the universe — at least that part of the budget that gives rise to electromagnetic radiation. Neutrino and gravitational radiation background measurements would be required before a complete ledger could be set up.

We have carried out near infrared observations on wide fields of the sky, using both a rocket-borne telescope and ground-based equipment. The rocket observations covered the spectral range of 1 to 8 μm. The ground-based observations were carried out in a narrow spectral region around 1.085 μm. The rocket observations give increased sensitivity over a previous flight carried out by one of us in collaboration with D. P. McNutt, K. Shivanandan and B. J. Zajac of the U.S. Naval Research Laboratory. We observe a general signal which would not have been detected in our previous flight. This new signal appears to be genuine, but because of a number of difficulties, mainly associated with vent gases, we prefer not to trust these signals until we have been able to carry out a confirming flight. We will, in the present paper, use the observed fluxes as an upper limit to the near infrared radiation incident on the top of the atmosphere.

The design and performance of a liquid-He-cooled spectrometer being developed for the Kuiper Airborne Observatory (KAO) to study FIR lines originating in the interstellar medium are discussed. Currently, the spectrometer contains six Ge:Ga photoconductor detectors mounted in integrating cavities and cooled to about 3 K; the collimator focal plane has space for 39 such detectors. The instrument achieves a maximum resolving power of 6000 by means of a 45-cm long echelle grating and is optically capable of operating in the spectral range 25-300 microns. A laboratory spectrum of water vapor, an atmospheric water absorption feature measured from the KAO with Mars as a source, and the forbidden O(2+) emission from W51-IRS1 are shown.

The article discusses the geodesic motion of photons, considering particularly whether oppositely polarized photons fall at the same rate. It is assumed that orthogonally polarized photons would be equally deflected by the gravitational field of a nonrotating mass. Upon the introduction of rotation, the angular momentum of the deflecting source couples to the photon spin through gravitational field action. Thus there arise separate trajectories for orthogonal polarizations. Searching for changes in polarization in a deflected beam is accomplished by a relative phase delay technique. If the beam is split into orthogonal linear polarization, final polarization is elliptical. Experiments have been performed on searching for ellipticity developments in the linearly polarized carrier waves from Helios 1 and 2, and the results are presented.

It is generally assumed that the potential scope of any scientific discipline is quite incalculable. Yet the discovery of the Earth's major rivers, mountains and seas, an enterprise that may have seemed endless to Ptolemy's contemporaries, is now essentially complete. The same may soon be said about the discovery of new plants and animals on Earth1. Harwit2,3 has put forward a procedure for estimating the number of observational phenomena remaining to be discovered in astronomy. Here we describe a statistical approach which supports the conclusion that the number of phenomena already discovered represents an appreciable fraction of those that can can be found.

Limb darkening on earth night side observed by Aerobee rocket, with explanation based on atmospheric opacity in water vapor and carbon dioxide bands

This final chapter describes various applications and potential applications of Hadamard transform optical techniques. The techniques are still new and are only just beginning to find their way into general use. We have therefore restricted the discussion to examples which will indicate the wide range of potential applications. Some of these are at present just speculations. Further applications will no doubt occur to the reader.

A first requirement for the establishment of a cosmic distance scale is the correct measurement of distances within the solar system. The basic step in this procedure is the measurement of the distance to Venus. The most precise way of obtaining this distance is through the use of radar techniques. Another method is described in problems 2–2 and 2–3 at the end of this chapter.

In the past few years, NASA's Kuiper Airborne Observatory (KAO) has made it possible to conduct pioneering observations of far infrared lines from astronomical sources. Such observations, in the case of wavelengths in the approximate range from 20 to 350 microns, cannot be performed from ground-based sites, because of telluric water absorption effects. Lines in the considered range provide information about the interstellar gas in molecular, neutral atomic, and ionized form of occurrence. The present paper provides a description of the development of the cryogenic optical system of a spectrometer designed to exploit the potential of the KAO for observing the far infrared lines. Attention is given to design goals and considerations, details of optical design, the fabrication of the optical system, the cryostat, and performance.

Spectroscopic instruments are designed to divide radiation into its component wavelengths (or frequencies) and to provide the observer with a display of this information at high signal-to-noise ratio (SNR).

In preceding chapters we discussed the appearance of stars and stellar systems and we looked in some detail at the immediate surroundings of the sun, the one star to which we have easy access. Now we want to examine the environment in which the sun, the stars, and the stellar systems are embedded. We want to learn about the properties of the universe.