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The development of oceanography and meteorology has greatly benefited from satellite-based data of Earth’s atmosphere and ocean. Traditional Earth observation missions have utilised Sun-synchronous orbits with repeat ground tracks due to their advantages in visible and infrared wavelengths. However, diversification of observation wavelengths and massive deployment of miniaturised satellites are both enabling and necessitating new kinds of space missions. This paper proposes several unconventional satellite orbits intended for use in, but not limited to, Earth observation. This ‘toolbox’ of orbits and taxonomy thereof will thus support the definition of design requirements for the individual satellites in nano-satellite constellations developed by national space agencies, industries and academia.

This paper focuses on the existence and control of particular types of orbits around asteroid 4 Vesta, including Sun-synchronous orbits, orbits at the critical inclination, repeating ground-track orbits, and stationary orbits. J2, J3, and J4 terms are considered in the gravity model of Vesta. First, the inclination perturbation caused by solar gravitation is studied, and preset and multiple inclination bias methods are proposed to dampen the local time drift at the ascending node. Compared with Vesta, the control periods of the Sun-synchronous orbits of 21 Lutetia and 433 Eros are much longer. Second, Vesta’s orbits with a critical inclination depend on the semi-major axis and eccentricity. If the eccentricity is not greater than 0.2, inclination decreases slowly and monotonically concerning the semi-major axis. If the eccentricity is not smaller than 0.4, inclination increases rapidly and monotonically. Third, Sun-synchronous repeating ground-track circular orbits of Vesta, which do not exist for Lutetia and Eros, are investigated. Finally, the perturbations of stationary orbits caused by solar gravitation and solar radiation pressure are analyzed.

With the development of aerospace science and technology, more and more probes are expected to be deployed around extraterrestrial planets. In this paper, some special orbits around Jupiter, Saturn, Uranus, and Neptune are discussed and analyzed. The design methods of some special orbits are sorted out, considering the actual motion parameters and main perturbation forces of these four planets. The characteristics of sun-synchronous orbits, repeating ground track orbits, and synchronous planet orbits surrounding these plants are analyzed and compared. The analysis results show that Uranus does not have sun-synchronous orbits in the general sense. This paper also preliminarily calculates the orbital parameters of some special orbits around these planets, including the relationship between the semi-major axis, the eccentricity and the orbital inclination of the sun-synchronous orbits, the range of the regression coefficient of the sun-synchronous repeating ground track orbits, and the orbital parameters of synchronous planet orbits, laying a foundation for more accurate orbit design of future planetary probes.

A method for the integrated analysis and the determination of the composite construction parameters of a platform of the Earth remote sounding spacecraft, is proposed. The conditions of thermal load for a flight along a sun-synchronous orbit were analysed. The mathematical simulation of the operating conditions ensuring the effective operation of such satellites was performed. The method was tested with account of the input parameters of the «BelKA» satellite orbit. This method will be useful when selecting a working orbit for such satellites at the stage of technical proposals, since it includes determination of their orbital characteristics, as well as the heat flows onto the elements of their construction. The results of simulation of thermal regime of the composite structure options are presented.

Frozen orbits and Sun-synchronous orbits are useful in exploration of terrestrial planets’ surface and atmosphere with a view to future human exploration. This work therefore develops novel orbits around terrestrial planets using continuous low-thrust propulsion to enable one new and unique investigations of the planets. This paper considers the use of continuous acceleration by solar electric propulsion, to achieve artificial frozen orbits and artificial Sun-synchronous orbits around terrestrial planets. These artificial orbits are similar to natural frozen orbits and Sun-synchronous orbits around Mercury, Venus, the Earth, and Mars, and the orbital parameters can be designed arbitrarily with the help of continuous low-thrust control. The control strategies to achieve the artificial orbits take into account J 2 , J 3 , and J 4 perturbations of terrestrial planets. It is proved that the control strategies minimize characteristic velocity. Relevant formulas are derived, and numerical results are presented. For the natural frozen orbits, the arguments of periapsis are about 270° for Mercury, Venus, and Mars, whereas about 90° for the Earth. By exerting both radial and transverse thrusts simulation shows that the control acceleration and characteristic velocity of the artificial frozen orbit around Mercury are the smallest among these plants. The characteristic velocity within one orbital period for Mercury is only 0.0089 m/s. The natural Sun-synchronous orbits exist around the Earth and Mars, but not around Mercury and Venus. By offsetting the perturbation acceleration in norm direction, the control acceleration and characteristic velocity of the artificial Sun-synchronous orbit around Mars are less than those of the others. The characteristic velocity within one orbital period is only 18.0885 m/s for the artificial Sun-synchronous orbit around Mars. The relationships between the control thrusts and the primary orbital parameters of the artificial orbits around other terrestrial planets are always similar to those around the Earth. Finally, one constellation of the artificial frozen orbit and the artificial Sun-synchronous orbit is designed by using the multiobjective evolutionary algorithm based on decomposition (MOEA/D), in which a Gaussian process is used to build a surrogate model in lieu of the expensive problem. Simulation shows that the control scheme effectively extends the orbital parameters’ selection ranges of the two types of artificial orbits around terrestrial planets, compared with the natural frozen orbit and Sun-synchronous orbit. The optimization result of the constellation orbits around Mars shows that the optimization framework is effective.

For the operationally responsive space mission with the known launch point and target area, based on the simplified trajectory, the design method of the sun-synchronous orbit is given by the orbit dynamics, considering the mutually constrained relationship between the satellite orbit and the launch vehicle trajectory. Then, with the orbit parameters as the input, the trajectory model obtains the actual trajectory parameters. Considering the error between the actual and simplified trajectory parameters, the actual trajectory parameters are used to correct the simplified trajectory. Finally, by iterative calculation, the parameters of sun-synchronous orbit and launch vehicle trajectory for operationally responsive space are obtained with the finite trajectory error. For a typical example, the parameters are calculated by the method, which is verified by the STK simulation, demonstrating the feasibility and practicability of the method. The design method can provide theoretical support for the orbit and trajectory design of operationally responsive space.

The Hα line is an important optical line in solar observations containing the information from the photosphere to the chromosphere. To study the mechanisms of solar eruptions and the plasma dynamics in the lower atmosphere, the Chinese Hα Solar Explorer (CHASE) was launched into a Sun-synchronous orbit on October 14, 2021. The scientific payload of the CHASE satellite is the Hα Imaging Spectrograph (HIS). The CHASE/HIS acquires, for the first time, seeing-free Hα spectroscopic observations with high spectral and temporal resolutions. It consists of two observational modes. The raster scanning mode provides full-Sun or region-of-interest spectra at Hα (6559.7–6565.9 Å) and Fe I (6567.8–6570.6 Å) wavebands. The continuum imaging mode obtains full-Sun photospheric images at around 6689 Å. In this paper, we present detailed calibration procedures for the CHASE/HIS science data, including the dark-field and flat-field correction, slit image curvature correction, wavelength and intensity calibration, and coordinate transformation. The higher-level data products can be directly used for scientific research.

There is a rapid growth of national space launch ambitions and capabilities, e.g. delivering satellites into low-earth and sun-synchronous orbits. With vertical and horizontal delivery methods, and numerous locations under consideration in several continents, the industry has faced early challenges, such as failed launches and licencing timescales. This paper explores the increasing intersection between aviation and air traffic management (ATM) with higher airspace operations (HAOs). It introduces the background and principles of space launches, before addressing the particular impacts on aviation and ATM. The strategic challenges of planning launch windows to align both with orbiting asset congestion and ATM demands, plus promulgating such information to airspace users, is discussed. In the tactical phase, the consequences of impacts on airspace users (such as the re-routing of flights) and on air navigation service providers (such as the demands of coordinating airspace closures in the context of considerable re-entry/splashdown uncertainty) are discussed. A key contribution we make in this paper is the first aircraft-specific, fuel and operating cost analysis of HAO impacts, and the first such European cost assessment, with basic impact geometries. We also propose improved aircraft-specific impact models, which include passenger-centric costs.

NUSES is a pathfinder for new satellite platforms developed by THALES and cutting-edge photo sensing technologies, such as SiPM and their associated low-power-consuming electronics. It is financed by the Italian Ministry and conducted by the Gran Sasso Science Institute (GSSI), INFN sections and the University of Geneva. NUSES hosts two payloads: Ziré is devoted to low-energy cosmic rays to investigate aspects related to space weather, and gamma-rays from gamma-ray bursts; the Terzina telescope will achieve the first observation from space of the Cherenkov light emitted by atmospheric showers induced by ultra-high-energy cosmic rays (UHECRs) within its field of view. Terzina might catch also a few Earth-skimming neutrinos above about 100 PeV. This faint light may only be detected by Terzina from a sun-synchronous orbit at 535 km of altitude while pointing to the limb and viewing the dark side of the earth and atmosphere. In such a configuration, this space-based telescope would not be constrained by the day-night cycle, unlike ground-based Cherenkov telescopes or payloads in non-polar orbit. Terzina is a Schmidt-Cassegrain telescope with dual mirror optics with a 935 mm effective focal length and a primary mirror with a diameter of 430 mm. Its SiPM-based camera is composed of 2 rows of 5 tiles of 8 × 8 SiPM 3x3 mm 2 pixels. The University of Geneva collaborated with the FBK Research Foundation to define these tiles. We measured in the laboratory the equivalent effect of radiation in space on the SiPM. Understanding the light noise in situ is vital for future larger missions or constellations of such satellites in the plans in the US and Europe and also for other missions employing SiPMs. For this study we utilized a 50 MeV proton beam and a beta-radioactive source of Strontium-90. As a matter of fact, radiation damage increases the DCR, and consequently to keep the signal-to-noise ratio constant the trigger threshold has to be increased. However, we developed an annealing approach suitable for a space-based middle-size satellite to limit the effect of radiation damage while efficiently lowering the SiPM’s energy detection threshold.

The Sentinel-5 Precursor satellite was successfully launched on 13 October 2017, carrying the Tropospheric Monitoring Instrument (TROPOMI) as its single payload. TROPOMI is the next-generation atmospheric sounding instrument, continuing the successes of GOME, SCIAMACHY, OMI, and OMPS, with higher spatial resolution, improved sensitivity, and extended wavelength range. The instrument contains four spectrometers, divided over two modules sharing a common telescope, measuring the ultraviolet, visible, near-infrared, and shortwave infrared reflectance of the Earth. The imaging system enables daily global coverage using a push-broom configuration, with a spatial resolution as low as 7×3.5 km2 in nadir from a Sun-synchronous orbit at 824 km and an Equator crossing time of 13:30 local solar time. This article reports the pre-launch calibration status of the TROPOMI payload as derived from the on-ground calibration effort. Stringent requirements are imposed on the quality of on-ground calibration in order to match the high sensitivity of the instrument. A new methodology has been employed during the analysis of the obtained calibration measurements to ensure the consistency and validity of the calibration. This was achieved by using the production-grade Level 0 to 1b data processor in a closed-loop validation set-up. Using this approach the consistency between the calibration and the L1b product, as well as confidence in the obtained calibration result, could be established. This article introduces this novel calibration approach and describes all relevant calibrated instrument properties as they were derived before launch of the mission. For most of the relevant properties compliance with the calibration requirements could be established, including the knowledge of the instrument spectral and spatial response functions. Partial compliance was established for the straylight correction; especially the out-of-spectral-band correction for the near-infrared channel needs future validation. The absolute radiometric calibration of the radiance and irradiance responsivity is compliant with the high-level mission requirements, but not with the stricter calibration requirements as the available on-ground validation shows. The relative radiometric calibration of the Sun port was non-compliant. The non-compliant subjects will be addressed during the in-flight commissioning phase in the first 6 months following launch.