首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 796 毫秒
1.
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, Cl,15andSl,15 in the usual notation. These equations (together with eight constraint equations) are solved to give:
  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 l, C?l,15 and S?l,15 in the usual notation. The recommended solution, going up to l = 31, is:
l109Cl,15109Sl,15
16?13.7 ± 1.3?18.5 ± 2.7
18?42.3 ± 1.8?34.7 ± 3.4
2010.5 ± 3.129.8 ± 5.2
22?8.6 ± 3.8?20.2 ± 7.4
  相似文献   

3.
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°:
l109C?l,15109S?l,15
15?21.5 ± 0.9?8.4 ± 0.9
174.4 ± 1.69.0 ± 1.5
19?15.6 ± 2.6?14.1 ± 2.7
2110.4 ± 3.07.3 ± 3.5
2322.5 ± 2.81.2 ± 4.4
25?0.9 ± 4.7?3.8 ± 5.3
27?11.2 ±3.39.1 ± 3.2
29?20.5 ± 5.4?1.2 ± 6.1
3117.7 ± 6.6?1.0 ± 7.1
  相似文献   

4.
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, C?l,15 and S?l,15 (with l = 15, 17, 19, …) in the usual notation. Our analysis gives values of these coefficients up to l = 33 as follows:
Feb 1958 to mid 19601.5 rev/day
Mid 1960 to Dec 19671.2 rev/day
Jan 1968 to Mar 19701.3 rev/day
  相似文献   

5.
The Earth's gravitational potential is now usually expressed in terms of a double series of tesseral harmonics with several hundred terms, up to order and degree at least 20. The harmonics of order 14 can be evaluated by analysing changes in satellite orbits which experience 14th-order resonance, when the track over the Earth repeats after 14 revolutions.In this paper we describe our first evaluation of individual 14th-order coefficients in the geopotential from analysis of the variations in inclination and eccentricity of satellite orbits passing through 14th-order resonance under the action of air drag. Using results from eleven satellites, we find the following values for normalized coefficients of harmonics of order 14 and degree l, C?l, 14 and S?l, 14, for l=14, 154. 22:
l109C?l,15109S?l,15
15?23.5 ± 0.8?7.7 ± 0.8
176.3 ± 1.55.6 ± 1.5
19?25.1 ± 2.5?7.3 ± 2.3
2127.8 ± 3.6?0.7 ± 3.4
2317.1 ± 4.113.9 ± 4.8
25?1.1 ± 3.08.5 ± 4.2
2710.0 ± 3.36.7 ± 2.7
29?9.4 ± 3.50.1 ± 4.7
3110.1 ± 5.43.8 ± 5.6
331.1 ± 5.73.1 ± 5.8
  相似文献   

6.
  相似文献   

7.
  相似文献   

8.
We have investigated Bianchi type III non-static magnetized cosmological model for perfect fluid distribution in general relativity. We assume that F 12 is the only non-vanishing component of F ij . Maxwell’s equation
l109C?l,14109S?l,14
---
14?38.5 ±2.9?7.8 ±2.2
154.5 ±1.1?23.8 ±0.3
16?22.3 ±3.6?36.0 ±3.8
17?15.0 ±2.616.8 ±1.2
18?24.0±4.9?3.2 ±3.7
19?1.6 ±2.8?7.6 ±1.0
208.8 ±5.8?15.4 ±4.6
2118.2 ±3.6?10.6 ±1.9
22?14.5 ±8.19.9 ±6.4
leads to
where K and α are constants. To get a deterministic model, we assume that σ 11 ∝ θ which leads to A=C n where n is a constant, σ 11 the x-component of shear tensor σ ij and theta is the expansion in the model. The behaviour of the model in absence of magnetic field is discussed. The other physical and geometrical aspects of the model are also discussed.  相似文献   

9.
《Experimental Astronomy》2009,23(1):435-461
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.
Charles S. CockellEmail:
  相似文献   

10.
Recently it has been shown that the relatively low closure temperature (Tc) of 500 (100)°C calculated for augite from Miller Range nakhlite (MIL 03346,13) using the available geothermometers would correspond to a slow cooling rate inconsistent with the petrologic evidence for an origin from a fast‐cooled lava flow. Moreover, previous annealing experiments combined with HR‐SC‐XRD on an augite crystal from MIL 03346 clearly showed that at 600 °C, the Fe2+‐Mg degree of order remained unchanged, thus suggesting that the actual Tc is close to this temperature. In order to clarify this discrepancy, we undertook an ex situ annealing experimental study at 700, 800, and 900 °C, until the equilibrium in the intracrystalline Fe2+‐Mg exchange is reached, using an augite crystal from Miller Range nakhlite (MIL 03346,13) with a composition of about En36Fs24Wo40. These data allowed us to calculate the following new geothermometer calibration for Martian nakhlites: where The application of this new equation to other Martian nakhlites (NWA 988 and Nakhla) suggests that for augite with composition close to that of MIL 03346, the Tc is up to 170 °C higher with respect to the one calculated using the previous available geothermometer equation, thus suggesting a significantly faster cooling in agreement with petrologic evidence.  相似文献   

11.
Speckle interferometric observations made with the 6 m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences in 2000 revealed the triple nature of the nearby (π Hip = 51.80 ± 1.74 mas) low-mass young (≈ 200 Myr) star GJ 900. The configuration of the triple system allowed it to be dynamically unstable. Differential photometry performed from 2000 through 2004 yielded I- and K-band absolute magnitudes and spectral types for the components to be I A =6.66±0.08, I B =9.15±0.11, I C =10.08±0.26, K A =4.84±0.08, K B =6.76±0.20, K C =7.39±0.31, Sp A ≈K5?K7, Sp B ≈M3?M4, Sp C ≈M5?M6. The “mass-luminosity” relation is used to estimate the individual masses of the components: M A ≈0.64M ⊙, M B ≈0.21M ⊙, M C ≈0.13M ⊙. From the observations of the components’ relative motion in the period 2000–2006, we conclude that GJ 900 is a hierarchical triple star with the possible orbital periods PA-BC≈80 yrs and PBC≈20 yrs. An analysis of the 2MASS images of the region around GJ 900 leads us to suggest that the system can include other very-low-mass components.  相似文献   

12.
The POLAR Investigation of the Sun (POLARIS) mission uses a combination of a gravity assist and solar sail propulsion to place a spacecraft in a 0.48 AU circular orbit around the Sun with an inclination of 75° with respect to solar equator. This challenging orbit is made possible by the challenging development of solar sail propulsion. This first extended view of the high-latitude regions of the Sun will enable crucial observations not possible from the ecliptic viewpoint or from Solar Orbiter. While Solar Orbiter would give the first glimpse of the high latitude magnetic field and flows to probe the solar dynamo, it does not have sufficient viewing of the polar regions to achieve POLARIS’s primary objective: determining the relation between the magnetism and dynamics of the Sun’s polar regions and the solar cycle.
T. AppourchauxEmail:
  相似文献   

13.
It has been shown (Heggie, 1974) that the equations of motion for the three-body problem may be cast into a form which is regular for collisions betweenany pair of bodies. The method proceeds by two stages, namely
(i)  the introduction of redundant variables
(ii)  the application of the KS-transformation.
The present contribution gives a different treatment of the first of these stages, and relates the redundant variables to those introduced by Broucke and Lass (1973).  相似文献   

14.
The non-linear stability of L 4 in the restricted three-body problem has been studied when the bigger primary is a triaxial rigid body with its equatorial plane coincident with the plane of motion. It is found that L 4 is stable in the range of linear stability except for three mass ratios:
where A1, A2 depend upon the lengths of the semi axes of the triaxial rigid body. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

15.
The non-linear stability of the libration pointL 4 in the restricted problem has been studied when there are perturbations in the potentials between the bodies. It is seen that the pointL 4 is stable for all mass ratios in the range of linear stability except for three mass ratios depending upon the perturbing functions. The theory is applied to the following four cases:
(i)  There are no perturbations in the potentials (classical problem).
(ii)  Only the bigger primary is an oblate spheroid whose axis of symmetry is perpendicular to the plane of relative motion (circular) of the primaries.
(iii)  Both the primaries are oblate spheroids whose axes of symmetry are perpendicular to the plane of relative motion (circular) of the primaries.
(iv)  The primaries are spherical in shape and the bigger is a source of radiation.
  相似文献   

16.
PEGASE is a mission dedicated to the exploration of the environment (including habitable zone) of young and solar-type stars (particularly those in the DARWIN catalogue) and the observation of low mass companions around nearby stars. It is a space interferometer project composed of three free flying spacecraft, respectively featuring two 40 cm siderostats and a beam combiner working in the visible and near infrared. It has been proposed to ESA as an answer to the first “Cosmic Vision” call for proposals, as an M mission. The concept also enables full-scale demonstration of space nulling interferometry operation for DARWIN.
M. OllivierEmail:
  相似文献   

17.
An attempt is made to study the relations between emergence of active regions and the solar background large-scale structures on the basis of Solar Geophysical Data, including Kitt-Peak magnetograms, H filtergrams, and Ca images.The emergence of 217 active regions (a.r.s) that have appeared on the solar disk not farther than ± 60° from the central meridian is studied. The a.r.s are divided into two classes A and B according to their birth location. Class A contains a.r.s emerged far (8–10°) from the background field boundaries, and class B- those emerged near to (55°) or just at the boundaries.It was found that a.r.s of class A differ appreciably from those of class B; in particular, the dimensions and the intensity (S, I) of class B a.r.s are nearly twice as large as those of class A. For class A a.r.s some alterations of the solar large-scale structure boundaries were found in 15% of all the cases, whereas for those of class B in 60%.  相似文献   

18.
In this paper we present new and exact analytical and computational developments of Güttler's formulae for composite grains, thereafter applied for the two models:
(1)  Graphite core-ice mantle.
(2)  Silicate core-ice mantle.
Literal and analytical expressions have been established for the Riccati-Bessel of the complex functions n , n , and n and their derivatives. The problem is treated in its general form without any restriction and the computer programme is now ready for request.  相似文献   

19.
The Space Infrared telescope for Cosmology and Astrophysics (SPICA) is planned to be the next space astronomy mission observing in the infrared. The mission is planned to be launched in 2017 and will feature a 3.5 m telescope cooled to <5 K through the use of mechanical coolers. These coolers will also cool the focal plane instruments thus avoiding the use of consumables and giving the mission a long lifetime. SPICA’s large, cold aperture will provide a two order of magnitude sensitivity advantage over current far infrared facilities (>30 microns wavelength). We describe the scientific advances that will be made possible by this large increase in sensitivity and give details of the mission, spacecraft and focal plane conceptual design.
Bruce SwinyardEmail:
  相似文献   

20.
The purpose of this paper is to find correlation between OI 6300 Å line intensity with solar and ionospheric parameters. A critical study have been made and the following important results are obtained:
(i)  Solar flare index plays more important role for the emissions of 6300 Å line than other solar parameters.
(ii)  Intensity of 6300 Å line increases linearly with the increase of solar flare index.
(iii)  Virtual height plays more important role than critical frequency for the emission of 6300 Å line-intensity.
(iv)  Possible explanation of this type of variation is also presented.
  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号