Object image linking of earth orbiting objects in the presence of cosmics

In survey series of unknown Earth orbiting objects, no a priori orbital elements are available. In surveys of wide field telescopes possibly many non-resolved object images are present on the single frames of the series. Reliable methods have to be found to associate the object images stemming from the same object with each other, so-called linking. The presence of cosmic ray events, so-called Cosmics, complicates reliable linking of non-resolved images. The tracklets of object images allow to extract exact positions for a first orbit determination.     

Field and wave measurements aboard the Aureol-3 spacecraft

In the Soviet-French Arcad-3 project, 3 experiments TBF-ONCH, TRAC and ISOPROBE are carried out on board the Aureol-3 satellite to measure the AC and DC electric and magnetic fields and waves. Several modes of telemetry, real time and memory regimes are available for data transmission. TBF-ONCH is devoted to the measurement of 3 components of the DC electric field, 2 electric and 3 magnetic components of the waves. In one mode of the real time telemetry these 5 components are transmitted simultaneously in the frequency range 10 Hz-1.5 kHz in order to be able to determine the wave normal directions of natural emissions and to localize their sources. In the second mode, morphological studies of saucers, chorus, hiss and triggered emissions can be undertaken using the wide band transmission (70 Hz-16 kHz) of any one of these 5 components with the possibility of periodically changing the transmitted component every 4 seconds or keeping the same one during all the pass. TRAC makes use of the on board 3 axis flux gate magnetometer to perform a fine measurement of the magnetic effects of the currents flowing in the vicinity of the spacecraft either in the ionosphere or along the magnetic field lines, with a resolution of ～ 12 nT and in the frequency range from DC to ～ 20 Hz. One component of the HF electric field (0.1–10 Mhz) is measured by ISOPROBE (see companion paper). Examples of inflight measurements from the above instruments and their presentation on microfiches are shown. Some new phenomena are emphasized and briefly discussed.     

载波相位/捷联惯导组合对高轨飞行器的导航

高轨飞行器可用卫星数目较少,信号空间链路损耗大,使用伪距进行测量的精度较低.提出基于GNSS(Global Navigation Satellite System)卫星载波相位与捷联惯导紧组合方法对高轨机动飞行器进行自主导航.该方法将连续跟踪的卫星初次可用时的整周模糊度的浮点解作为状态变量,通过平方根UKF建立了组合导航非线性滤波模型,提出了基于整周浮点解交集的滤波器故障检测方法.研究表明,提出的组合导航方法充分利用了载波相位高测量精度和系统性误差缓变的特点,提高了系统的可靠性和精度.     

Modification of plant growth and development by acceleration and vibration: concerns and opportunities for plant experimentation in orbiting spacecraft.

Growth, development, and orientation of higher plants is altered by physical disturbances such as shaking, touching, or vibration. Plant growth responses to thigmic (contact rubbing) forces are almost always negative, whereas growth responses to periodic seismic (shaking) or vibric (vibrational) disturbances may be positive or negative, depending on intensity and duration of force, and prevailing environmental conditions. Seedlings are most sensitive to mechanical stress when grown in darkness or under the low-light conditions typically available in plant flight hardware. Brief exposure to physical perturbation causes immediate growth inhibition of dark-grown seedlings followed by gradual recovery of growth rate beginning 10-12 minutes later. For mild vibration, growth rate may overshoot that of undisturbed control plants within an hour of a stress episode, whereas for thigmic stress recovery may remain incomplete for 24 hours or longer. Lack of physical stimulation by gravity should make plants even more responsive to random physical perturbation. Threshold growth response of seedlings to vibrational parameters needs to be determined under real spaceflight conditions.     

Characteristics of cosmic ray cutoffs for a satellite orbiting at 400 km; The effect of the solid earth

Studies of galactic cosmic ray intensity and composition by means of earth orbiting space vehicles often rely on the earth's magnetic field as a momentum analyzer or threshold energy indicator. We have determined, by the trajectory-tracing process, cosmic ray cutoff characteristics for a satellite at 400 km altitude. These calculations indicate that cosmic rays have direct access to the satellite from the magnetic west down to angles of 135° from the zenith. For spacecraft observations it is necessary to employ additional definitions of cutoff beyond the classical Stormer definition because there are regions with allowed orbits where the cutoff, in the classical sense, does not exist.     

Testing relativity with orbiting clocks

We describe the background and status of a superconducting microwave clock suitable for relativity experiments in earth orbit. The project has the capability of performing improved tests of Lorentz invariance via a Michelson–Morley type experiment, and setting new limits on nine parameters in the Standard Model Extension. If flown with a high stability atomic clock, a Kennedy–Thorndike experiment along with additional tests in general relativity could be performed.     

基于航天器解体事件的空间碎片寿命算法

研究了针对航天器解体事件所生成的空间碎片的寿命计算方法.给出了基于NASA标准航天器解体模型的航天器解体算法.该算法生成的一系列碎片参数,将作为寿命计算的初始条件.总结了现有求解碎片寿命的算法,并提出了一种半分析算法.该算法运用平均根数法的思路,计算了在J2摄动项的影响下,碎片的半长轴和偏心率的变化率;并采用微分积分法预报半长轴和偏心率随时间的变化.为了适应时变大气模型,该算法限制了计算步长.通过与数值法的比较分析了算法的计算速度和精度.选用了3种大气模型:SA76、GOST和MSIS-00,分析了不同大气模型在计算碎片寿命之间的差异.通过与P-78卫星解体事件的实测数据对比验证了整个算法的正确性.      

The impact of dust grains on fast fly-by spacecraft: Momentum multiplication,measurements and theory

Energy partitioning during the very high impact speed encountered in a cometary fly-by mission causes a target mass expulsion which leads to a momentum impulse on the target exceeding that of the incident momentum. Theoretical and computational studies are required to provide a basis for predictions of the response at Halley encounter, since experimental data from acceleration of microspheres extends currently only to some 10 kms^?1. Such data obtained from the 2 MV Canterbury microparticle accelerator is presented: this demonstrates a target momentum enhancement E which can be approximated by a form E = 1+(V/V_o)^β. Over the range 1 to 8 kms^?1 the relationship is satisfied by V_o = 2 kms^?1 and β = 2. Theoretical considerations of energy partitioning lead to constraints on the extrapolation of this functional dependence to very high velocities and the transition to β ≤ 1 is shown to apply. Results are examined and their significance to impact sensing and spacecraft deceleration discussed. An enhancement of momentum nearer to 12±3 at 69 kms^?1 is anticipated for non-penetrating particles, from the ballistic pendulum data, but the ES data indicates a figure considerably higher.     

Particle and optical measurements aboard the Aureol 3 spacecraft (ARCAD 3 project): A — The particle experiments B — Optical measurements

The CESR Toulouse - IKI Moscow particle instrument package aboard the AUREOL-3 satellite consists of a complete set of charged particle spectrometers which measure electron and ion fluxes from 15 eV to 25 keV in 128 steps and in 11 directions. In addition, 4 channel spectrometers (2 electron and 2 ion channels in parallel) allow high time resolution measurements (up to 10 msec) with onboard calculation of auto and cross correlation functions. For higher energies (40 – 280 keV), solid-state spectrometers are used to measure electron and proton fluxes in 4 channels in parallel. In addition, two Geiger counters are used for the determination of the trapping boundaries. Two mass-energy ion spectrometers (1 to 32 A.M.U., 0.02 – 15 keV) are placed with viewing angles which allow a distinction between nearly isotropic auroral proton precipitation and conical beams accelerated in the auroral ionosphere. Auroral and airglow photometry is performed aboard the AUREOL-3 satellite by a set of 3 parallel directed photometers with tiltable interference filters for 6300 Å, 4278 Å and Doppler shifte H_β emissions. Various modes of energy, angular and mass scanning, correlation function calculation and various Soviet and French telemetry regimes provide the possibility of choosing the sequences of measurements according to particular experimental programs along the orbit. Finally, examples of data from inflight measurements using the above instruments are presented and briefly discussed, showing several interesting features.     

Long-term monitoring of stratospheric temperature trends using radiance measurements obtained by the TIROS-N series of NOAA spacecraft

In order to determine longterm trends in stratospheric temperature from observations by a series of satellite radiometers, it is necessary to establish the reproducibility and systematic drifts in both the radiometric and the spectroscopic performance of successive instruments. The practical limitations on long term temperature monitoring imposed by current operational designs are illustrated with time series of data from both the Stratospheric Sounding Unit (SSU) and Microwave Sounding Unit (MSU) on the TIROS-N series of NOAA spacecraft.     

Attitude control actuator scaling laws for orbiting solar reflectors

The rapid evolution of in-orbit manufacturing will enable the fabrication of low-cost, large-scale space structures. In particular, the use of 3D printing technologies will remove traditional payload constraints associated with launch vehicles, due to fairing size and launch loads, thus allowing the construction of larger and lighter structures, such as orbiting solar reflectors. These structures will require efficient attitude control systems, able to provide the necessary torque for maneuvers and to counteract perturbations, such as gravity gradient and solar radiation pressure. In this paper, a top-level overview of actuator performances for orbiting solar reflectors is provided, and scaling laws associated with the required actuator mass and input power are developed. For each class of actuator, upper bounds on the maximum size of the structure which can be effectively controlled are presented. The results can also be extended to other classes of large planar Earth-pointing structures such as solar power satellites, solar sails, or large antennae.     

Digital spacecraft ionosondes

In cooperation with RCA, Astro-Electronics Division, a digital spacecraft ionosonde has been developed and its prototype built by ULCAR. On-board use of the Direct Discrete Fourier Transform for signal-to-noise enhancement, suppression of unwanted echoes and the identification of echo properties permit several applications. In ionospheric topside satellites (>800 km above ground) the ionospheric profile over all parts of the earth will be measured with simple and new data compression techniques on board of the satellite. Digital data preprocessing overcomes the breakthrough of ground-based man-made interference and analyzes auroral and equatorial echoes. Because the ionosonde measures amplitude, phase, Doppler, range and polarization of a radio wave simultaneously, it will be a very useful tool for the Waves in Space Plasma program of the NASA Space Shuttle, especially for a mother-daughter configuration. With a synchronized transmitter on the ground, such a Digisonde in a low-flying satellite (100–400 km) can receive signals from ducted radio waves launched into the ionosphere near natural or artificial ionization depletion areas for the study of large distance radiowave propagation.     

Wave and plasma measurements on the Vega-1 and Vega-2 spacecraft in the environment of comet Halley

The Vega-1 and Vega-2 wave and plasma measurements performed on 6 and 9 March 1986 in the environment of comet Halley present similar characteristics. Field spectral intensity of up to $\text{5}\text{mVm}{}^{\mathrm{?1}}\text{Hz}{}^{\mathrm{?}}\text{1}\text{2}$ at 300 Hz is measured at closest approach; enhanced signals are detected in the whistler mode and in the vicinity of the lower hybrid resonance frequency within respective average distances of 130,000 km and 60,000 km from the nucleus. The plasma density rises from 100 cm^?3 at 200,000 km up to 3000 cm^?3 at 25,000 km. The spacecraft potential is of the order of +3 V beyond a distance of 200,000 km and decreases to about +0.5 V at 8,000 km.     

Very low thrust station-keeping for low Earth orbiting satellites

Traditional station-keeping for Earth observation satellites with chemical thrusters generally involves maneuvers every couple months that are able to change significantly the semi-major axis and the inclination. These strategies do not scale down to very low thrust level (a few hundreds of μN) electrical thrusters. This paper presents both in-plane and out-of-plane strategies that spread corrections over very long arcs and discretize them to tiny maneuvers every couple orbits, taking into account mission-constraints on maneuvers locations. These strategies scale up to medium thrust strategies, filling the gap between propulsion technologies. The out-of-plane strategy although features a new no-deadband property and controls the full orbital momentum. All strategies allow control very close to the reference (a few hundreds meters in osculating parameters) and very low cost.     

GPS single-frequency orbit determination for low Earth orbiting satellites

The determination of high-precision orbits for Low Earth Orbiting (LEO) satellites (e.g., CHAMP, GRACE, MetOp-A) is based on dual-frequency tracking data from on-board GPS (Global Positioning System) receivers. The two frequencies allow it to eliminate the first order ionosphere effects. Data screening and precise orbit determination (POD) procedures are optimized under the assumption of the availability of two frequencies.     

Faster algorithm of debris cloud orbital character from spacecraft collision breakup

Space debris is polluting the space environment. Collision fragment is its important source. NASA standard breakup model, including size distributions, area-to-mass distributions, and delta velocity distributions, is a statistic experimental model used widely. The general algorithm based on the model is introduced. But this algorithm is difficult when debris quantity is more than hundreds or thousands. So a new faster algorithm for calculating debris cloud orbital lifetime and character from spacecraft collision breakup is presented first. For validating the faster algorithm, USA 193 satellite breakup event is simulated and compared with general algorithm. Contrast result indicates that calculation speed and efficiency of faster algorithm is very good. When debris size is in 0.01–0.05 m, the faster algorithm is almost a hundred times faster than general algorithm. And at the same time, its calculation precision is held well. The difference between corresponding orbital debris ratios from two algorithms is less than 1% generally.     

基于矢量观测的航天器分段信息融合定姿方法

针对基于MEMS(微机电系统)陀螺和CMOS APS星敏感器的集成惯性/星光姿态确定系统的低精度特点,研究了适用于该定姿系统的基于矢量观测的定姿算法.对于陀螺/星敏感器这种配置模式,有EKF(Extended Kalman Filter)、QUEST、最优REQUEST等几种适用的定姿算法.针对EKF和最优REQUEST算法的不同特点并结合确定性算法QUEST,以四元数为姿态参数,将姿态估计的EKF方法分别与QUEST算法和最优REQUEST算法进行了融合,提出一种分段信息融合的姿态估计器:陀螺漂移估计误差较大时,将EKF与QUEST结合,快速估计出陀螺漂移.当陀螺漂移误差减小到一定程度,再切换为EKF与最优REQUEST算法融合的双重滤波器.仿真比较结果表明,这种分段信息融合的姿态估计器既可以估计姿态参数也可以估计陀螺漂移,并能达到很高的定姿精度.     

Climatic variations in the outgoing longwave radiation of the past decade as observed from NOAA polar orbiting satellites

Components of the earth radiation budget have been calculated on a regular basis since June 1974 (except for a 10 month gap in data in 1978) based on measurements by the scanning radiometers and the advanced very high resolution radiometers on the operational NOAA polar orbiting satellites. A new base set of monthly and seasonal averages of outgoing longwave radiation has been prepared by NOAA's Climate Analysis Center (CAC) for the entire period of record through November 1983. Anomalies relative to these new normals have now been constructed for each month and season in the entire record.In this presentation, some of the more prominent anomalies of outgoing longwave radiation over the past decade are discussed. A major concentration is on the tropics and subtropics where there have been very substantial radiation variations associated with major shifts in convective cloudiness accompanying El Niño/Southern Oscillation events.