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1.
We have analysed the variations of inclination in 13 satellite orbits as they pass slowly, under the action of air drag, through 15th-order resonance with the geopotential, when successive equatorial crossings are 24° apart and the ground track repeats after 15 rev. The size and form of the change in inclination are determined mainly by the values of the geopotential harmonics of 15th order and odd degree, and (with l = 15, 17, 19, …) in the usual notation. Our analysis gives values of these coefficients up to l = 33 as follows: | l | 109C?l,15 | 109S?l,15 | | 15 | ?23.5 ± 0.8 | ?7.7 ± 0.8 | | 17 | 6.3 ± 1.5 | 5.6 ± 1.5 | | 19 | ?25.1 ± 2.5 | ?7.3 ± 2.3 | | 21 | 27.8 ± 3.6 | ?0.7 ± 3.4 | | 23 | 17.1 ± 4.1 | 13.9 ± 4.8 | | 25 | ?1.1 ± 3.0 | 8.5 ± 4.2 | | 27 | 10.0 ± 3.3 | 6.7 ± 2.7 | | 29 | ?9.4 ± 3.5 | 0.1 ± 4.7 | | 31 | 10.1 ± 5.4 | 3.8 ± 5.6 | | 33 | 1.1 ± 5.7 | 3.1 ± 5.8 | 相似文献
2.
When a satellite orbit decaying slowly under the action of air drag experiences 15th-order resonance with the Earth's gravitational field, so that the ground track repeats after 15 rev, the orbital inclination suffers appreciable changes due to the perturbations from the harmonics in the geopotential of order 15 and odd degree (15,17,19 …). In this paper the changes in inclination at resonance of 11 satellites at inclinations between 30° and 90° have been analysed to determine values of the geopotential coefficients of order 15 and degree and in the usual notation. The recommended solution, going up to l = 31, is: | l | 109C?l,15 | 109S?l,15 | | 15 | ?21.5 ± 0.9 | ?8.4 ± 0.9 | | 17 | 4.4 ± 1.6 | 9.0 ± 1.5 | | 19 | ?15.6 ± 2.6 | ?14.1 ± 2.7 | | 21 | 10.4 ± 3.0 | 7.3 ± 3.5 | | 23 | 22.5 ± 2.8 | 1.2 ± 4.4 | | 25 | ?0.9 ± 4.7 | ?3.8 ± 5.3 | | 27 | ?11.2 ±3.3 | 9.1 ± 3.2 | | 29 | ?20.5 ± 5.4 | ?1.2 ± 6.1 | | 31 | 17.7 ± 6.6 | ?1.0 ± 7.1 | 相似文献
3.
When a satellite orbit decaying slowly under the action of air drag experiences 15th-order resonance with the Earth's gravitational field, so that the ground track repeats after 15 rev, the orbital eccentricity may suffer appreciable changes due to perturbations from the gravitational harmonics of order 15 and even degree (16, 18, 20…). In this paper the changes in eccentricity at resonance for six satellites in near-circular orbits at inclinations between 56 and 90° have been analysed to derive 11 pairs of equations linking the harmonic coefficients of order 15 and (even) degree l, in the usual notation. These equations (together with eight constraint equations) are solved to give: | 109 | 109 | | 16 | ?13.7 ± 1.3 | ?18.5 ± 2.7 | | 18 | ?42.3 ± 1.8 | ?34.7 ± 3.4 | | 20 | 10.5 ± 3.1 | 29.8 ± 5.2 | | 22 | ?8.6 ± 3.8 | ?20.2 ± 7.4 | 相似文献
4.
Explorer 1, 1958α, ths first U.S. artificial satellite, was launched on 1 February 1958 and remained in orbit for 12 years. In this paper theoretical curves have been fitted to the values of inclination, giving three values of the average atmospheric rotation rate at heights of 350–400 km, and latitudes 0–20°: | Feb 1958 to mid 1960 | 1.5 rev/day | | Mid 1960 to Dec 1967 | 1.2 rev/day | | Jan 1968 to Mar 1970 | 1.3 rev/day | 相似文献
6.
The Earth's gravitational potential is usually expressed as an infinite series of tesseral harmonics, and it is possible to evaluate “lumped harmonics” of a particular order m by analyses of resonant satellite orbits—orbits with tracks over the Earth that repeat after m revolutions. In this paper we review results on 30th-order harmonics from analyses of 15th-order resonance, and results on 29th- and 31st-order harmonics from 29:2 and 31:2 resonance.The values available for 30th-order lumped harmonics of even degree are numerous enough to allow a solution for individual coefficients of degree up to 40. The best-determined coefficients are those of degree 30, namely The standard deviations here are equivalent to 1 cm in geoid height.For the 29th- and 31st-order harmonics, and for the 30th-order harmonics of odd degree, there are not enough values to determine individual coefficients, but the lumped values from particular satellites can be used for “resonance testing” of gravity field models, particularly the Goddard Earth Model 10B (up to degree 36) and 10C (for degree greater than 36). The results of applying these tests are mixed. GEM 10B/C emerges well for order 30, with s.d. about 3×10 ?9; for order 31, the GEM 10B values are probably good but the GEM 10C values are probably not; for order 29, the test is indecisive. 相似文献
7.
As part of a continuing series of experiments on the production of dark reddish organic solids, called tholins, by irradiation of cosmically abundant reducing gases, the synthesis from a simulated Titanian atmosphere of a tholin with a visible reflection spectrum similar to that of the high altitude aerosols responsible for the albedo and reddish color of Titan has been reported Sagan and Khare, 1981, Sagan and Khare, 1982, Orig. Life. 12, 280) and [C. Sagan, B. N. Khare, and J. Lewis, in press. In Saturn (M. S. Matthews and T. Gehrels, Eds.), Univ. of Arizona Press, Tucson]. The determination of the real ( n) and imaginary ( k) parts of the complex refractive index of thin films of such tholin prepared by continuous D.C. discharge through a 0.9 N 2/0.1 CH 4 gas mixture at 0.2 mb are reported. For have been determined from a combination of transmittance, specular reflectance, interferometric, Brewster angle, and ellipsometric polarization measurements; experimental uncertainties in n are estimated to be ±0.5, and in k ± 30%. Values of n(?1.65) and k (?0.004 to 0.08) in the visible range are consistent with deductions made by ground-based and spacecraft observations of Titan. Maximum values of k (?0.8) are near 1000 Å, and minimum values (?4 × 10 ?4) are near 1.5 μm. Many infrared absorption features are present in k( γ), including the 4.6-μm nitrile band. 相似文献
10.
We have selected and analyzed a sample of OB stars with known line-of-sight velocities determined through ground-based observations and with trigonometric parallaxes and propermotions from the Gaia DR2 catalogue. Some of the stars in our sample have distance estimates made from calcium lines. A direct comparison with the trigonometric distance scale has shown that the calcium distance scale should be reduced by 13%. The following parameters of the Galactic rotation curve have been determined from 495 OB stars with relative parallax errors less than 30%: ( U, V,W) ⊙ = (8.16, 11.19, 8.55)± (0.48, 0.56, 0.48) km s ?1, Ω 0 = 28.92 ± 0.39 km s ?1 kpc ?1, Ω' 0 = ?4.087 ± 0.083 km s ?1 kpc ?2, and Ω″ 0 = 0.703 ± 0.067 km s?1 kpc ?3, where the circular velocity of the local standard of rest is V0 = 231 ± 5 km s ?1 (for the adopted R0 = 8.0 ± 0.15 kpc). The parameters of the Galactic spiral density wave have been found from the series of radial, V R, residual tangential, ΔV circ, and vertical, W, velocities of OB stars by applying a periodogram analysis. The amplitudes of the radial, tangential, and vertical velocity perturbations are fR = 7.1± 0.3 km s ?1, fθ = 6.5 ± 0.4 km s ?1, and fW = 4.8± 0.8 km s ?1, respectively; the perturbation wavelengths are λR = 3.3 ± 0.1 kpc, λθ = 2.3 ± 0.2 kpc, and λW = 2.6 ± 0.5 kpc; and the Sun’s radial phase in the spiral density wave is (χ ⊙) R = ?135? ± 5?, (χ ⊙) θ = ?123? ± 8?, and (χ ⊙) W = ?132? ± 21? for the adopted four-armed spiral pattern. 相似文献
11.
We consider two samples of OB stars with different distance scales that we have studied previously. The first and second samples consist of massive spectroscopic binaries with photometric distances and distances determined from interstellar calcium lines, respectively. The OB stars are located at heliocentric distances up to 7 kpc. We have identified them with the Gaia DR1 catalogue. Using the proper motions taken from the Gaia DR1 catalogue is shown to reduce the random errors in the Galactic rotation parameters compared to the previously known results. By analyzing the proper motions and parallaxes of 208 OB stars from the Gaia DR1 catalogue with a relative parallax error of less than 200%, we have found the following kinematic parameters: ( U, V) ⊙ = (8.67, 6.63)± (0.88, 0.98) km s ?1, Ω 0 = 27.35 ± 0.77 km s ?1 kpc ?1, Ω′ 0 = ?4.13 ± 0.13 km s ?1 kpc ?2, and Ω″ 0 = 0.672 ± 0.070 km s ?1 kpc ?3, the Oort constants are A = ?16.53 ± 0.52 km s ?1 kpc ?1 and B = 10.82 ± 0.93 km s ?1 kpc ?1, and the linear circular rotation velocity of the local standard of rest around the Galactic rotation axis is V 0 = 219 ± 8 km s ?1 for the adopted R 0 = 8.0 ± 0.2 kpc. Based on the same stars, we have derived the rotation parameters only from their line-of-sight velocities. By comparing the estimated values of Ω′ 0, we have found the distance scale factor for the Gaia DR1 catalogue to be close to unity: 0.96. Based on 238 OB stars of the combined sample with photometric distances for the stars of the first sample and distances in the calcium distance scale for the stars of the second sample, line-of-sight velocities, and proper motions from the Gaia DR1 catalogue, we have found the following kinematic parameters: ( U, V, W) ⊙ = (8.19, 9.28, 8.79)± (0.74, 0.92, 0.74) km s ?1, Ω 0 = 31.53 ± 0.54 km s ?1 kpc ?1, Ω′ 0 = ?4.44 ± 0.12 km s ?1 kpc ?2, and Ω″ 0 = 0.706 ± 0.100 km s ?1 kpc ?3; here, A = ?17.77 ± 0.46 km s ?1 kpc ?1, B = 13.76 ± 0.71 km s ?1 kpc ?1, and V 0 = 252 ± 8 km s ?1. 相似文献
12.
Open star clusters from the MWSC (Milky Way Star Clusters) catalogue have been used to determine the Galactic rotation parameters. The circular rotation velocity of the solar neighborhood around the Galactic center has been found from data on more than 2000 clusters of various ages to be V 0 = 236 ± 6 km s ?1 for the adopted Galactocentric distance of the Sun R 0 = 8.3 ± 0.2 kpc. The derived angular velocity parameters are Ω 0 = 28.48 ± 0.36 km s ?1 kpc ?1, Ω’ 0 = ?3.50 ± 0.08 km s ?1 kpc ?2, and Ω″ 0 = 0.331 ± 0.037 km s ?1 kpc ?3. The influence of the spiral density wave has been detected only in the sample of clusters younger than 50 Myr. For these clusters the amplitudes of the tangential and radial velocity perturbations are f θ = 5.6 ± 1.6 km s ?1 and f R = 7.7 ± 1.4 km s ?1, respectively; the perturbation wavelengths are λ θ = 2.6 ± 0.5 kpc ( i θ = ?11? ± 2?) and λ R = 2.1 ± 0.5 kpc ( i R = ?9? ± 2?) for the adopted four-armed model ( m = 4). The Sun’s phase in the spiral density wave is (χ ⊙) θ = ?62? ± 9? and (χ ⊙) R = ?85? ± 10? from the residual tangential and radial velocities, respectively. 相似文献
13.
A sample of classical Cepheids with known distances and line-of-sight velocities has been supplemented with proper motions from the Gaia DR1 catalogue. Based on the velocities of 260 stars, we have found the components of the peculiar solar velocity vector ( U, V, W) ⊙ = (7.90, 11.73, 7.39) ± (0.65, 0.77, 0.62) km s ?1 and the following parameters of the Galactic rotation curve: Ω 0 = 28.84 ± 0.33 km s ?1 kpc ?1, Ω′ 0 = ?4.05 ± 0.10 km s ?1 kpc ?2, and Ω″ 0 = 0.805 ± 0.067 km s ?1 kpc ?3 for the adopted solar Galactocentric distance R 0 = 8 kpc; the linear rotation velocity of the local standard of rest is V 0 = 231 ± 6 km s ?1. 相似文献
14.
As a response to ESA call for mission concepts for its Cosmic Vision 2015–2025 plan, we propose a mission called Darwin. Its primary goal is the study of terrestrial extrasolar planets and the search for life on them. In this paper, we describe
different characteristics of the instrument.
相似文献
16.
We consider stars with radial velocities, proper motions, and distance estimates from the RAVE4 catalogue. Based on a sample of more than 145 000 stars at distances r < 0.5 kpc, we have found the following kinematic parameters: \({\left( {U,{\kern 1pt} V,{\kern 1pt} W} \right)_ \odot }\) = (9.12, 20.80, 7.66) ± (0.10, 0.10, 0.08) km s ?1, Ω 0 = 28.71 ± 0.63 km s ?1 kpc ?1, and Ω 0 ’ = ?4.28 ± 0.11 km s ?1 kpc ?2. This gives the linear rotation velocity V 0 = 230 ± 12 km s ?1 (for the adopted R 0 = 8.0 ± 0.4 kpc) and the Oort constants A = 17.12 ± 0.45 km s ?1 kpc ?1 and B = ?11.60 ± 0.77 km s ?1 kpc ?1. The 2D velocity distributions in the UV, UW, and VW planes have been constructed using a local sample, r < 0.25 kpc, consisting of ~47 000 stars. A difference of the UV velocity distribution from the previously known ones constructed from a smaller amount of data has been revealed. It lies in the fact that our distribution has an extremely enhanced branch near the Wolf 630 peak. A previously unknown peak at ( U, V) = (?96, ?10) km s ?1 and a separate new feature in the Wolf 630 stream, with the coordinates of its center being ( U, V) = (30, ?40) km s ?1, have been detected. 相似文献
17.
Based on high-latitude molecular clouds with highly accurate distance estimates taken from the literature, we have redetermined the parameters of their spatial orientation. This systemcan be approximated by a 350 × 235 × 140 pc ellipsoid inclined by the angle i = 17° ± 2° to the Galactic plane with the longitude of the ascending node l Ω = 337° ± 1°. Based on the radial velocities of the clouds, we have found their group velocity relative to the Sun to be ( u 0, v 0, w 0) = (10.6, 18.2, 6.8) ± (0.9, 1.7, 1.5) km s ?1. The trajectory of the center of the molecular cloud system in the past in a time interval of ~60 Myr has been constructed. Using data on masers associated with low-mass protostars, we have calculated the space velocities of the molecular complexes in Orion, Taurus, Perseus, and Ophiuchus. Their motion in the past is shown to be not random. 相似文献
20.
Absolute spectrophotometry of Neptune from 3390 to 7800 Å, with spectral resolution of 10 Å in the interval 3390–6055 and 20 Å in the interval 6055–7800 Å, is reported. The results are compared with filter photometry ( Appleby, 1973; Wamsteker, 1973; Savage et al., 1980) and with synthetic spectra computed on the basis of a parameterization proposed by Podolak and Danielson (1977) for aerosol scattering and absorption. A CH 4/H 2 ratio of is derived for the convectively mixed part of Neptune's atmosphere, and constrains optical properties of hypothetical aerosol layers. 相似文献
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