Impact of orbit modeling on DORIS station position and Earth rotation estimates

The high precision of estimated station coordinates and Earth rotation parameters (ERP) obtained from satellite geodetic techniques is based on the precise determination of the satellite orbit. This paper focuses on the analysis of the impact of different orbit parameterizations on the accuracy of station coordinates and the ERPs derived from DORIS observations. In a series of experiments the DORIS data from the complete year 2011 were processed with different orbit model settings. First, the impact of precise modeling of the non-conservative forces on geodetic parameters was compared with results obtained with an empirical-stochastic modeling approach. Second, the temporal spacing of drag scaling parameters was tested. Third, the impact of estimating once-per-revolution harmonic accelerations in cross-track direction was analyzed. And fourth, two different approaches for solar radiation pressure (SRP) handling were compared, namely adjusting SRP scaling parameter or fixing it on pre-defined values.     

The role of the united nations in promoting international cooperation in peaceful uses of outer space

The Committee on the Peaceful Uses of Outer Space (COPUOS) was established in 1959 by the United Nations General Assembly in order to review and foster international cooperation in the peaceful uses of outer space and to consider legal issues arising from the exploration of outer space. Since its establishment, the Committee has addressed such issues as benefits from space activities, the definition and delimitation of outer space and the use of the geostationary orbit, implications of remote sensing, space sciences, space-based communications, navigation and meteorological systems, as well as use of nuclear power sources in outer space, space debris and spin-off benefits of space technology. At its session in 1996, a symposium on the ‘Utilization of micro- and small satellites for the expansion of low-cost space activities, taking into particular account the needs of developing countries’ was organized by COSPAR and IAF to complement discussions on this theme. It was noted at the symposium that the increasing number of small satellites, in particular the proposed introduction of multi-satellite ‘constellations’ at low orbits, would result in concentrations of satellite mass at certain regions of space around the Earth. Special provisions would be needed to minimize the probability of satellite breakups and collisions which might create more space debris and compromise the future of spaceflight.     

Czechs in space

This is a nutshell history of the Czech nation's long-standing interest, and achievements, in space science, technology and education. It attempts to show that despite difficult periods, this country has always been able to bring up new ideas and contribute to progress of sciences. The current transition into market economy, democratic society, and preparation for integration into the European Union is one of those difficult periods. However, given the determination of its people, and proven past record, it has all the prerequisites again to contribute significantly to future space exploration on a global scale, and return to the forefront of technology and science.     

The IAA Cosmic Study on space traffic management

This is a slightly edited version of the IAA's recently published interdisciplinary and international study on managing the traffic—of all manifestations—in outer space. The study examines the requirements and prospects for managing space traffic in the future and provides a thorough analysis of the status of ways and means of doing so, as well as a comprehensive to-do list for organizations like COPUOS and ICAO.     

Response of the mesopause temperatures to solar activity over Yakutia in 1999–2013

OH(6-2) rotational temperature trends and solar cycle effects are studied. Observations were carried out at the Maimaga station (63.04°N, 129.51°E) for the period August 1999 to March 2013. Measurements were conducted with an infrared spectrograph. Temperatures were determined from intensity ratios in the P branch of the OH band. The monthly average residuals of temperature after the subtraction of the mean seasonal variation were used for a search for the solar component of temperature response. The dependence of temperatures on solar activity has been investigated using the Ottawa 10.7 cm flux as a proxy. A linear regression fitting on residual temperatures yields a solar cycle coefficient of 4.24 ± 1.39 K/100 solar flux units (SFU). The cross-correlation analyses showed that changes of the residual temperature follow changes of solar activity with a quasi-two year delay (25 months). The temperature response at the delay of 25 months reaches 7 K/100 SFU. The possible reason of the observed delay can be an influence of quasi-biennial oscillations (QBO) of the atmosphere on the relation of temperature and solar activity. The value of the temperature trend after the subtraction of seasonal and solar components is not statistically significant.     

Solar Ultraviolet Bursts

The term “ultraviolet (UV) burst” is introduced to describe small, intense, transient brightenings in ultraviolet images of solar active regions. We inventorize their properties and provide a definition based on image sequences in transition-region lines. Coronal signatures are rare, and most bursts are associated with small-scale, canceling opposite-polarity fields in the photosphere that occur in emerging flux regions, moving magnetic features in sunspot moats, and sunspot light bridges. We also compare UV bursts with similar transition-region phenomena found previously in solar ultraviolet spectrometry and with similar phenomena at optical wavelengths, in particular Ellerman bombs. Akin to the latter, UV bursts are probably small-scale magnetic reconnection events occurring in the low atmosphere, at photospheric and/or chromospheric heights. Their intense emission in lines with optically thin formation gives unique diagnostic opportunities for studying the physics of magnetic reconnection in the low solar atmosphere. This paper is a review report from an International Space Science Institute team that met in 2016–2017.