Search

The apparent magnitude of a complex shaped space object is difficult to calculate since its visible triangular facets are hard to be determined. The most common-used visible facets determination method is to judge the incident and emergent angle, but this method does not apply to a space object which is a combination of convex bodies or has a concave surface. In this paper, a new quadtree-based hidden vertex removal method is presented, and it is composed of four steps: coordinate transformation, hidden vertex removal, quadtree decompositions and visible triangular facets determination. This method can determine visible triangular facets of a space object of any shapes. Once a space object triangular facet model, the observed direction of a telescope and the incident direction of the sunlight are given, the visible triangular facets of the space object can be obtained. Two experiments are carried out to verify the visible triangular facet determination performance of this method qualitatively and quantitatively. Experiment results show the visible triangular facet calculated by the proposed method is accurate and reasonable.

We tackle the problem of accurate optical tracking of distant man-made probes, on Halo orbit around the Earth-Sun libration point L2 and beyond, along interplanetary transfers. The improved performance of on-target tracking, especially when observing with small-class telescopes is assessed providing a general estimate of the expected S/N ratio in spacecraft detection. The on-going Gaia mission is taken as a pilot case for our analysis, reporting on fresh literature and original optical photometry and astrometric results. The probe has been located, along its projected nominal path, within 0.13 +/- 0.09 arcsec, or 0.9 +/- 0.6 km. Spacecraft color appears to be red, with (V-R_c) = 1.1 +/- 0.2 and a bolometric correction to the R_c band of (Bol-R_c) = -1.1 +/- 0.2. The apparent magnitude, R_c = 20.8 +/- 0.2, is much fainter than originally expected. These features lead to suggest a lower limit for the Bond albedo a = 0.11 +/- 0.05 and confirm that incident Sun light is strongly reddened by Gaia through its on-board MLI blankets covering the solar shield. Relying on the Gaia figures, we found that VLT-class telescopes could yet be able to probe distant spacecraft heading Mars, up to 30 million km away, while a broader optical coverage of the forthcoming missions to Venus and Mars could be envisaged, providing to deal with space vehicles of minimum effective area Aeff >= 10^6 cm^2. In addition to L2 surveys, 2m-class telescopes could also effectively flank standard radar-ranging techniques in deep-space probe tracking along Earth's gravity-assist maneuvers for interplanetary missions., In press for Advances in Space Research (w/ 15 colour figures and 1 table)

We developed a general method for determination of water production rates from groundbased visual observations and applied it to Comet Hale–Bopp. Our main objective is to extend the method to include total visual magnitude observations obtained with CCD detector and V filter in the analysis of total visual magnitudes. We compare the CCD V-broadband careful observations of Liller [Liller, W. Pre-perihelion CCD photometry of Comet 1995 O1 (Hale-Bopp). Planet. Space Sci. 45, 1505–1513, 1997; Liller, W. CCD photometry of Comet C/1995 O1 (Hale-Bopp): 1995–2000. Int. Comet Quart. 23(3), 93–97, 2001] with the total visual magnitude observations from experienced international observers found in the International Comet Quarterly (ICQ) archive. A data set of ∼400 CCD observations covering about the same 6 years time span of the ∼12,000 ICQ selected total visual magnitude observations were used in the analysis. A least-square method applied to the water production rates, yields power laws as a function of the heliocentric distances for the pre- and post-perihelion phases. The average dimension of the nucleus as well as its effective active area is determined and compared with values published in the literature.

During the Leonid meteor shower on 18 November 1999, the five spectrographic imagers onboard the Midcourse Space Experiment (MSX) satellite recorded the first complete meteor spectra from 110 to 860 nm. The observation occurred at 00:23:36.2 UT, at which time satellite was pointed at a tangent altitude of 100 km over 37.2°N and 78.2°E. The spectrograph slits were oriented approximately parallel to the horizon, and the meteor passed approximately perpendicular through the slits’ fields of view. All five spectrographic images serendipitously observed the passage of the object and each recorded 1–2 frames of data. Common meteor emissions from iron, sodium, and oxygen were observed in the visible, but the ultraviolet spectrum displayed a wealth of new features. The most intense features appeared in the middle ultraviolet (250–300 nm) from neutral and singly ionized iron and singly ionized magnesium. Far ultraviolet (110–130 nm) features included oxygen and nitrogen, a bright hydrogen Lyman α emission, and ionized iron and magnesium emissions. Also seen in the far ultraviolet were weak but recognizable emissions from neutral carbon. The ultraviolet emissions were much stronger than those in the visible and near-infrared. The meteor had a visual magnitude of −2.8 at 100 km, but the energy of emissions in the ultraviolet (110–337 nm) exceeded the energy of the visible (337–560 nm) by a factor of at least 5. The new Lyman α and carbon emissions in the far UV as well as the overall intensity of the ultraviolet spectrum suggest important applications for ultraviolet observations of meteors.

A telescope employing a liquid metal (mercury) mirror that is three meters in diameter was developed for the purpose of measuring the population of small orbital debris. The telescope is installed at a 9,000 ft site in the mountains of New Mexico at a latitude of 32.98 degrees, and has completed final optical performance tests. A Ford 2048 × 2048 CCD detector is used at the image plane. With this detector, the limiting stellar magnitude of the telescope was measured to be 23 at a S/N of about 3, with a nominal full width, half maximum for stellar images of 1.3 arcsec. Safety problems with toxic mercury vapor were minimal at operating temperatures below 60 F, greatly simplifying operations with the mirror. Performance of the telescope for debris at geosynchronous orbit (GEO) altitudes is estimated to be in the range 5 to 10 cm using the existing CCD detector. However, at its present location in New Mexico, the telescope cannot be used for detection of debris in the GEO region, since it cannot see debris with inclinations below 32 degrees. Performance of the telescope for debris in low earth orbit depends on the kind of detector that is used. Efforts were made to use the CCD detector for fast-moving low earth orbit debris by reading out the detector at the same rate and in the same direction as the debris object crosses the field of view of the telescope. In this mode, the telescope was capable of detecting debris as small as 3 centimeters at 900 km altitude. However, this mode is very inefficient, since debris moving in other directions is not detected. Observations have also been done using an intensified CCD video camera as the detector. The limiting detectable size for this detector was about 4 centimeters at 500 km, and 7 centimeters at 1000 km. A design was developed for the optimum detector for fast-moving debris in low earth orbit based on currently available technology. This is a 1024×1024 element CCD detector operating at 200 frames per second, with pixels binned to 16×16. This detector should be capable of detecting 1 cm debris at 500 km and 1.5 cm debris at 1000 km. New data processing algorithms will be required to process the data stream from this detector.

The software for automatic extraction of double star parameters from Hipparcos data is tested for different types of star systems with different magnitudes, colours, separations and position angles. the influence of the mission degradation due to shorter available observation time is also examined, by checking the behaviour of the results depending on the number of observations of each star system.

Photographic, photometric and spectropolarimetric observations of SN 1987A made at the Pulkovo Observatory and Goloseevo Observatory Station in Bolivia are presented. The rate of brightness increase is ∼ 0. m 02 ≔ 0. m .03 per day during the period from 7 April 1987 to 15 May 1987. The intrinsic polarization of SN 1987A implies an assymetric shape of its envelope. These asymmetries are different in and out of the lines.

The results from the photometric observations of the x-ray source KR Aur for the period Oct. 1979 – Mai 1983 obtained at the National Astronomical Observatory, Bulgarian Acedemy of Sciences, are presented. The 1981 – 1982 minimum of the light curve is discussed.