Characterization of Lithium-Polymer batteries for CubeSat applications

With the development of several key technologies, nanosatellites are emerging as important vehicles for carrying out technology demonstrations and space science research. Nanosatellites are attractive for several reasons, the most important being that they do not involve the prohibitive costs of a conventional satellite launch. One key enabling technology is in the area of battery technology. In this paper, we focus on the characterization of battery technologies suitable for nanosatellites.Several battery chemistries are examined in order to find a type suitable for typical nanosatellite missions. As a baseline mission, we examine York University's 1U CubeSat mission for its power budget and power requirements. Several types of commercially available batteries are examined for their applicability to CubeSat missions. We also describe the procedures and results from a series of environmental tests for a set of Lithium Polymer batteries from two manufacturers.     

East–West Station-Keeping maneuver strategy for COMS satellite using iterative process

The first Korean multi-mission geostationary satellite, Communication, Ocean, and Meteorological Satellite (COMS) will be launched in 2010. The missions of this satellite will be Ka-band communications, ocean color monitoring, and meteorological imaging. The satellite was designed with only one solar array on the south panel. This novel configuration will keep imaging instruments on the north side from heating up. Asymmetry of the spacecraft configuration requires twice-a-day thruster-based Wheel Off-Loading (WOL) operations to keep the satellite attitude for imaging and communication. Thruster firings during the WOL operations cause the satellite orbit to change two times a day. Weekly East–West Station-Keeping (EWSK) and North–South Station-Keeping (NSSK) maneuver operations are planned for the COMS satellite in order to maintain the satellite in ±0.05° box at 128.2°E longitude.     

A study of long-term climatology of ionospheric irregularities by using GPS phase fluctuations at the Brazilian longitudes

We have examined the ionospheric plasma irregularities that were recorded by using three ground-based receivers of the global positioning system (GPS) located at Brazilian longitudes during the period of a complete solar cycle, 1995–2005. The statistic results show that ionospheric irregularities are very easy to occur in December solstice months but rare to occur in June solstice months. Besides, the occurrence rates of irregularities in both December and June solstice months are little dependent on solar activity. However, in equinoctial months, the development of irregularities is obviously dependent on solar activity. There is a new finding in this study that if strong irregularities are distinguished from moderate ones, their occurrence rates would increase with solar activity during the December solstice months.     

Legal analysis of Sea Launch license: National security and environmental concerns

This paper analyzes the national security and environmental concerns surrounding the Sea Launch consortium's international license from a legal perspective. The growing market demand for a more affordable, reliable, and convenient commercial satellite launching service has led to the idea of Sea Launch—launching satellites from the sea near the Equator. However, this can pose potential conflicts between national security and foreign policy interests, and between environmental conservation and economic growth because of the international technology development issues around launching from the sea. This paper illustrates a case for balancing such multiple constraints via legal interpretation. The analysis is conducted in reference to 49 U.S.C. § 70101–70119 Commercial Space Launch Activities and 42 U.S.C. § 4321–4345 National Environmental Policy Act (NEPA) of 1969. The paper also examines weather the United Nations Convention on the Law of the Sea is binding on Sea Launch operations. Although the scope of this paper is limited mostly to the US law and the national security and environmental aspects of Sea Launch, it provides a useful example for policy making of an international collaborative technology development project.     

Effects of solar activity variations on the low latitude topside nighttime ionosphere

We have studied the topside nighttime ionosphere of the low latitude region using data obtained from DMSP F15, ROCSAT-1, KOMPSAT-1, and GUVI on the TIMED satellite for the period of 2000–2004, during which solar activity decreased from its maximum. As these satellites operated at different altitudes, we were able to discriminate altitude dependence of several key ionospheric parameters on the level of solar activity. For example, with intensifying solar activity, electron density was seen to increase more rapidly at higher altitudes than at lower altitudes, implying that the corresponding scale height also increased. The density increased without saturation at all observed altitudes when plotted against solar EUV flux instead of F10.7. The results of the present study, as compared with those of previous studies for lower altitudes, indicate that topside vertical scale height increases with altitude and that, when solar activity increases, topside vertical scale height increases more rapidly at higher altitudes than at lower altitudes. Temperature also increased more rapidly at higher altitudes than at lower altitudes as solar activity increased. In addition, the height of the F2 peak was seen to increase with increasing solar activity, along with the oxygen ion fraction measured above the F2 peak. These results confirm that the topside ionosphere rises and expands with increasing solar activity.     

Adaptive Two-Stage Extended Kalman Filter for a Fault-Tolerant INS-GPS Loosely Coupled System

The well-known conventional Kalman filter requires an accurate system model and exact stochastic information. But in a number of situations, the system model has an unknown bias, which may degrade the performance of the Kalman filter or may cause the filter to diverge. The effect of the unknown bias may be more pronounced on the extended Kalman filter (EKF), which is a nonlinear filter. The two-stage extended Kalman filter (TEKF) with respect to this problem has been receiving considerable attention for a long time. Recently, the optimal two-stage Kalman filter (TKF) for linear stochastic systems with a constant bias or a random bias has been proposed by several researchers. A TEKF can also be similarly derived as the optimal TKF. In the case of a random bias, the TEKF assumes that the information of a random bi?s is known. But the information of a random bias is unknown or partially known in general. To solve this problem, this paper proposes an adaptive two-stage extended Kalman filter (ATEKF) using an adaptive fading EKF. To verify the performance of the proposed ATEKF, the ATEKF is applied to the INS-GPS (inertial navigation system-Global Positioning System) loosely coupled system with an unknown fault bias. The proposed ATEKF tracked/estimated the unknown bias effectively although the information about the random bias was unknown.     

Position-Domain Hatch Filter for Kinematic Differential GPS/GNSS

Motivated by the accuracy benefit of the Hatch gain compared with the Kalman-type gain and the advantage of position-domain (PD) filtering compared with range-domain (RD) filtering under frequent changes in visible satellite set, this paper proposes a PD Hatch filter for kinematic differential satellite-based positioning. It is shown that the Hatch gain generates white residual sequence in both the RD and the PD. An experiment result demonstrates that the proposed PD Hatch filter is advantageous in real-time kinematic positioning.     

酷路泽的时尚精神

丰田FJ酷路泽正式上市已经5个多月的时间了,其时尚前卫的个性、超凡的越野性能,为国内SUV市场增添了些许别样的风景。疯狂的越野迷们也与FJ酷路泽一同,挑战了种种险路阻途。FJ迷们表示,无论是在高温炙烤的沙漠中跋涉沙海,还是在风雪中破冰击雪,FJ酷路泽都能,以金刚般的意念勇往直前。     

A Review of Density Holes Upstream of Earth's Bow Shock

Larmor size transient structures with density depletions as large as 99% of ambient solar wind density levels occur commonly upstream of Earth＇s collisionless bow shock. These ＂density holes＂ have a me...     

Different mechanisms controlling interannual phytoplankton variation in the South China Sea and the western North Pacific subtropical gyre: A satellite study

A time series of remotely-sensed chlorophyll a (chl a) in 1997–2010 was evaluated to determine mechanisms of phytoplankton variation in recent decade in the South China Sea (SCS) and the western North Pacific subtropical gyre (WNPSG). Satellite-derived sea surface temperature (SST) and aerosol optical thickness (AOT) were used as proxies for vertical nutrient supply and atmospheric aerosol, respectively. Chl a in the WNPSG was not significantly correlated with SST (r = 0.18, p > 0.05), but was with AOT (r = 0.31, p < 0.05), indicating the chl a was influenced by atmospheric deposition. Chl a in the SCS was negatively correlated with SST (r = −0.60, p < 0.05) and was positively with AOT (r = 0.20, p < 0.05). The correlation between AOT and chl a in the SCS does not reflect a major contribution from atmospheric deposition to chl a; instead, the relationship resulted from concurrence of the peaks of AOT and wind speed, which drive water mixing and nutrient supply. Consequently, chl a in the SCS would be regulated primarily by the nutrient supply from deep waters. Because SST was controlled by the ENSO teleconnection in the SCS, the chl a was coupled with ENSO events. The present study demonstrated that interannual phytoplankton variation could be controlled by different factors even in neighboring oligotrophic regions.