Analysis of IRAS data for orbital debris

The Infrared Astronomical Satellite (IRAS) was launched in 1983 for the purpose of surveying the sky in a broad area of the infrared portion of the spectrum. While the primary objects of interest of IRAS were stars and nebulae, other types of space-related objects could also be observed. These include comets, asteroids, and Earth orbiting objects. Theoretical analysis indicates that IRAS could observe objects with a diameter of 1-mm at a range of 100-km and objects with a diameter of 1-cm at a range of 1000-km, while current ground-based observations of particles in low Earth orbit are limited to objects larger than 1-cm. Thus, these data offer a unique opportunity to ascertain the number density of particles below the present observable limit. At NASA/JSC a preliminary analysis of an IRAS data set has been performed to detect and describe this population, and the results of this study are presented.     

IRAS observations of cometary dust

The large beam size of the Infrared Astronomy Satellite (IRAS) focal plane detector array is well suited to measuring the low level thermal emission from cometary dust. Eight comets discovered in 1983 and nine previously known periodic comets were observed by IRAS during its ten month active lifetime. Dust production rates are derived for a wide range of heliocentric distances. Grain properties are inferred from application of simple models to the long wavelength spectral energy distribution.     

Dust optical properties: A comparison between cometary and interplanetary grains

A better understanding of cometary dust optical properties has been derived from extensive observations of comet Halley, complemented by other cometary observations at large phase angles and/or in the infrared. Also, further analysis of IRAS observations and improvements in inversion techniques for zodiacal light have led to some progress in our knowledge of interplanetary dust.

Synthetic curves for phase angle dependence of intensity and polarization are presented, together with typical albedo values. The results obtained for interplanetary dust are quite reminiscent of those found for comets. However, the heterogeneity of the interplanetary dust cloud is demonstrated by the radial dependence of its local polarization and albedo; these parameters are also found to vary with inclination of the dust grains' orbits with respect to the ecliptic. Such results suggest drastic alterations with temperature in the texture of cometary dust, and would favor an important asteroidal component in the zodiacal cloud.     

IRAS survey of asteroids

The Infrared Astronomical Satellite (IRAS) scanned the celestial sphere during 1983 through bandpasses centered at wavelengths of 12, 25, 60 and 100 microns. In addition to sources fixed on the sky, many moving objects, were also observed. This data set is the largest and least biased survey of asteroids and comets ever conducted. Included are main belt asteroids, Mars crossers, Earth approachers and Trojans. Measurements for the known asteroids have been reduced and organized into a number of data products which are available to researchers. The data for “new” asteroids are being processed. Output data products were specified at a series of IRAS Asteroid Workshops held in Pasadena over the past several years. In this paper we report on the current status of all of these data.     

Report on the Kiso cometary dust trail survey

Cometary dust trails were first observed by IRAS; they are widely known to be the origins of meteoric showers. A new window has been opened for the study of dust trails, using ground-based observations. We succeeded in obtaining direct images of the 22P/Kopff dust trail with the Kiso 1.05-m Schmidt telescope. Following this initial success, we have continued to perform a dust trail survey at Kiso. As a result of this survey, we have detected dust trails along the orbit of six periodic comets, between February 2002 and March 2004. The optical depth of these dust trails are 10⁻⁹ to 10⁻⁸, which is consistent with IRAS measurements. In this paper, we describe the observations and data reduction procedures, and report the brief result obtained between February 2002 and March 2004.     

Recent infrared observations of comets with UKIRT and IRAS

A preliminary analysis of infrared observations of comets P/Crommelin and P/Tempel 1 is presented. Comet P/Crommelin was observed from UKIRT over the range 1–20 micron, using standard filters. From the shape of the thermal emission spectrum, the temperature of the dust grains is estimated (T = 314 ± ₃₃⁴⁴K) and also the dust production rate (1.3 × 10⁵gs^?1). Comet P/Tempel 1 was observed with the Infrared Astronomical Satellite (IRAS). The emission is found to be considerably extended and there is also evidence for temperature variation of the dust grains as indicated by the 12 to 25 micron flux ratio.     

Silicate core-organic refractory mantle particles as interstellar dust and as aggregated in comets and stellar disks.

The principal observational properties of silicate core-organic refractory mantle interstellar dust grains in the infrared at 3.4 microns and at 10 microns and 20 microns are discussed in terms of the cyclic evolution of particles forming in stellar atmospheres and undergoing subsequent accretion, photoprocessing and destruction (erosion). Laboratory plus space emulation of the photoprocessing of laboratory analog ices and refractories are discussed. The aggregated interstellar dust model of comets is summarized. The same properties required to explain the temperature and infrared properties of comet coma dust are shown to be needed to account for the infrared silicate and continuum emission of the beta Pictoris disk as produced by a cloud of comets orbiting the star.     

Interstellar dust models

Interstellar dust models, previously constrained only from the extinction curve, have been radically changed with the arrival of IRAS observations of the dust infrared emission. An important component of interstellar dust is likely to be made of small particles that show a fluctuating temperature upon impinging single photons and which can produce large near and mid infrared excesses ubiquitously observed in the Galaxy and external galaxies. The analysis of COBE data should soon improve our understanding of dust infrared emissivity and particularly for big grains in the submillimeter domain. We will discuss the key observations (spectral features, broad-band colors, correlations with gas tracers…) which put the best constraints on any dust models and show that the next generation of IR/submm satellites (ISO, SIRTF…) should improve our knowledge of interstellar dust composition and the dust redistribution of the stellar energy inside galaxies.     

Infrared emission and optical scattering by the high galactic latitude dust cloud L1642

We present a comparison of optical surface brightness and extinction data with IRAS infrared maps at 60 and 100 μm for the high galactic latitude cloud L1642. We have derived the optical albedo of the grains and the ratio of 100 μm and optical opacities. The albedo does not depend strongly on wavelength; on the average the albedo is 0.5 between 3450 and 5500 Å. L1642 is detected also at 12 and 25 μm, where the morphology of the brightness distribution supports an explanation in terms of non-equilibrium emission from small grains and/or large aromatic molecules.     

Remote infrared observations of parent volatiles in comets: A window on the early solar system

Organic volatiles and water in Oort Cloud comets were investigated at infrared wavelengths. The detected species include H₂O, CO, CH₃OH, CH₄, C₂H₂, C₂H₆, OCS, HCN, NH₃, and H₂CO. Several daughter fragments (CN, OH, NH₂, etc.) are also measured, and OH prompt emission provides a proxy for water. Long-slit spectra are taken at high spectral dispersion and high spatial resolution, eliminating several sources of systematic error. The resulting parent volatile production rates are highly robust, permitting a sensitive search for compositional diversity among comets. Here, seven OC comets are compared. Six (including Halley) exhibit similar compositions (excepting CO and CH₄). Their low formation temperatures (30 K) suggest this group probably formed beyond 30 AU from the young sun. However, C/1999 S4 is severely depleted in hypervolatiles and also in methanol, and it likely formed near 5–10 AU. C/2001 A2 is discussed briefly to illustrate future prospects.     

A comparison of the dust properties in recent periodic comets

Measurements of the thermal emission from the cometary dust coma can be used to derive the rate of dust production from the nucleus as well as the size distribution of absorbing grains. More than ten short-period comets have now been observed in the infrared over a wide range in heliocentric distance. Dust production rates are derived for these comets based on theoretical models of the thermal emission from small absorbing grains and calculations of dust grain velocities. The mean size and albedo of the dust grains is similar in these comets, with the exception of Comet Crommelin, which seems to have had larger, darker grains.     

Ultraviolet spectroscopy of cometary comae: An update

Since its launch in 1978 the $\text{International Ultraviolet Explorer}$ ($\text{IUE}$) satellite observatory has been used to record ultraviolet spectra of nearly two dozen comets. These observations have been applied principally to studies of the composition, chemistry and evolution of the gaseous coma and more recently, with the substantially increased data base, to comparative analyses. The observations of Comets Bowell (1982 I) and Cernis (1983?) at a heliocentric distance of ≈ 3.4 AU show these two comets to be virtually identical and pose problems for water ice vaporization models. The most significant recent result from $\text{IUE}$ was the discovery of S₂ in the Earth-approaching comet IRAS-Araki-Alcock (1983d) and the use of the S₂ emission as a monitor of short-term variations in cometary activity. In early 1984, periodic comet Encke was observed for the second time by $\text{IUE}$, this time post-perihelion.     

等离子体彗星的某些相关分析

本文进行了彗星的分类统计,给出了"太刚活动"和"等离子体彗星出现频数"的统计,表示出它们之间无相关性。作了"太阳活动"与"彗星事件"的相关分析,表明其相关性是弱的;但是,"太阳风风速"与"彗星事件"的相关性较强。最后,用我国自己的资料作为一个实例,讨论了等离子体彗星的象差角及其扭折骚扰。      

彗星穿越过境对磁层的影响及其分析讨论

对哈雷、百武和海尔-波普三颗慧星在不同时间、不同位置的情况下5次过近地点可能引起对地球磁层影响进行了资料分析和统计研究，指出，根据等离子体彗尾的特征，完全可以对磁层引起扰动，但是这种扰动有严格的制约条件，不是每次彗星过境都很容易对地球电磁环境产生影响。     

Planned NASA space infrared astronomy experiments

A summary is presented of the present status of the NASA space infrared astronomy program. Projects described include the Infrared Astronomy Satellite (IRAS), Small Infrared Telescope on Spacelab 2 (IRT), Cosmic Background Explorer (COBE), Shuttle Infrared Telescope Facility (SIRTF), Space Telescope (ST), and the Large Deployable Reflector (LDR). The important technical developments achieved in these programs are also discussed, as well as critical needs for future missions.     

Survivability of biomolecules during extraterrestrial delivery: new results on pyrolysis of amino acids and poly-amino acids.

The hypothesis on exogenous origin of organic matter on the early Earth is strongly supported by the detection of a large variety of organic compounds (including amino acids and nucleobases) in carbonaceous chondrites. Whether such complex species can be successively delivered by other space bodies (comets, asteroids and interplanetary dust particles) is unclear and depends primarily on capability of the biomolecules to survive high temperatures during atmospheric deceleration and impacts to the terrestrial surface. Recent simulation experiments on amino acid and nucleic acid base pyrolysis under oxygen-free atmosphere demonstrated that simple representatives of these (considered thermally unstable) compounds can survive at 1-10% level a rapid heating at 500-600 degrees C. In the present work, we report on new data on the pyrolysis of amino acids and their homopolymers and discuss implications of their thermal behavior for extraterrestrial delivery.     

A laboratory study on the thermally induced transformation of hydrogen cyanide (HCN) to the cyanogen anion (CN) in Solar System analog ices

Mixtures of molecular nitrogen and methane have been identified in numerous outer Solar Systemices including the icy surfaces of Pluto and Triton. We have simulated the interaction of ionizing radiation in the Solar System by carrying out a radiolysis experiment on a methane – molecular nitrogen ice mixture with energetic electrons. We have identified the hydrogen cyanide molecule as the most prominent carbon–nitrogen-bearing reaction product formed. Upon warming the irradiated sample, we followed for the first time the kinetics and temporal evolution of the underlying acid–base chemistry which resulted in the formation of the cyanide ion from hydrogen cyanide. On the surfaces of Triton and Pluto and on comets in Oort’s cloud this sort of complex chemistry is likely to occur. In particular, hydrogen cyanide can be produced in low temperature environments (Oort cloud comets) and may be converted into cyanide ions once the comets reach the warmer regions of the Solar System.     

Cometary/meteor coupling: structure of young streams.

Information on atmospheric parameters, properties and processes above 70 km are mainly based upon meteor data. An important problem of such data systematization is to single out the meteor streams associated with a series of extreme phenomena. The forecasting of these phenomena requires a physical model of meteor streams at the early stage of their occurrence. A direct coupling with comets is assumed for most of the streams. This paper analyses the structure simulation of cometary nucleus desintegration. The D-criterion is used as the orbital community criterion. Giacobini-Zinner comet in its ten appearances (1900-1979) is considered. Determination of stream location and its detailed structural characteristics is essential for long space missions.     

IRAS observations of the zodiacal background

The Infrared Astronomical Satellite (IRAS) sky survey measurements are used to constrain a model for the interplanetary dust emission. Efforts to date, although hampered somewhat by calibration uncertainties, indicate that the cloud is inclined to the ecliptic by approximately 1.7° with its line of ascending nodes at 70° ecliptic longitude. The data is well fit by a dust density distribution described in cloud symmetry plane coordinates by p = p_o (r_o/r)^1.1 exp [−4.2 (z/r)^1.2], where the dust has a gray emissivity and an equilibrium temperature at 1 AU of 280 K.     

Localized properties of the zodiacal dust,by comparison of IRAS and of optical observations

The method of “the nodes of lesser uncertainty”, which led in the optical study of the zodiacal light to a fair localization of the information, is being adapted to the available thermal observations, especially to IRAS ones.The observations in the ecliptic plane give access to the temperature and, by comparison with optical results, to the albedo of the dust at 1 AU. The heliocentric derivatives are also obtained: the temperature decrease is slower than in a homogeneous cloud, and therefore the albedo is decreasing. If the apparent (optical) slope ν of the heliocentric fall r^−ν of the space density is corrected for this change of albedo, the true ν recovers a value close to 1, much more satisfying on theoretical grounds.This localization process allows to derive from the annual oscillations of brightness at the ecliptic poles the inclination and the ascending node of the symmetry plane of the zodiacal dust. After taking into account the eccentricity of the earth's orbit, IRAS data show a full agreement with previous ground-based (Tenerife) and satellite (D2A) results.