Estimation of ground range on the sweep frequency backscatter leading edge

The high frequency management system with backscatter radar supplies the real time ionosphere channel conditions to high frequency users, which leads to the demand for the ground range between the radar location and the scatters on the distant ground. The ionosphere electron density profile is usually inversed to obtain the ground range. An inversion algorithm, with which the ground range on the leading edge of the backscatter ionograms can be obtained without electron density, is presented in this paper. The ray path geometry of the backscatter sounding and the change in the group path on the leading edge with operating frequency are used to derive the ground range. Synthesized backscatter ionogram and experimental backscatter ionograms are processed to validate the algorithm. The results indicate that the algorithm is usable for high frequency management system.     

Comparison of peak characteristics of F2 ionospheric layer over Tehran region at a low solar activity period with IRI-2001 and IRI-2007 models predictions

In the present work values of peak electron density (NmF2) and height of F2 ionospheric layer (hmF2) over Tehran region at a low solar activity period are compared with the predictions of the International Reference Ionosphere models (IRI-2001 and IRI-2007). Data measured by a digital ionosonde at the ionospheric station of the Institute of Geophysics, University of Tehran from July 2006 to June 2007 are used to perform the calculations. Formulations proposed by  and  are utilized to calculate the hmF2. The International Union of Radio Science (URSI) and International Radio Consultative Committee (CCIR) options are employed to run the IRI-2001 and IRI-2007 models. Results show that both IRI-2007 and IRI-2001 can successfully predict the NmF2 and hmF2 over Tehran region. In addition, the study shows that predictions of IRI-2007 model with CCIR coefficient has closer values to the observations. Furthermore, it is found that the monthly average of the percentage deviation between the IRI models predictions and the values of hmF2 and NmF2 parameters are less than 10% and 21%, respectively.     

The Global Exploration Roadmap and its significance for NASA

The Global Exploration Roadmap reflects the collaborative effort of twelve space agencies to define a long-term human space exploration strategy which provides substantial benefits for improving the quality of life on Earth and is implementable and sustainable. Such a strategy is a necessary precondition to the government investments required to enable the challenging and rewarding missions that extend human presence into the solar system. The article introduces the international strategy and elaborates on NASA's leadership role in shaping that strategy. The publication of the roadmap, a reflection of the space landscape and multilateral agency-level dialog over the last four years, allows NASA to demonstrate its commitment to leading a long-term space exploration endeavor that delivers benefits, maintains strategic human spaceflight capabilities and expands human presence in space, with human missions to the surface of Mars as a driving goal. The road mapping process has clearly demonstrated the complementary interests of the participants and the potential benefits that can be gained through cooperation among nations to achieve a common goal. The present US human spaceflight policy is examined and it is shown that the establishment of a sustainable global space exploration strategy is fully consistent with that policy.     

Multiple-site investigation of the properties of an HF radio channel and the ionosphere using Digital Radio Mondiale broadcasting

The Digital Radio Mondiale (DRM), one of the new digital radio broadcasting standards, has been designed to overcome typical short wave radio channel difficulties, such as the multipath propagation and fast temporal changes of the received signal level, both related to the properties of the ionosphere along the path of propagation. In particular, some of the RF carriers used in the applied COFDM transmission technique serve to estimate the current state of the radio channel to enable the proper demodulation of the received signal.We have been detecting such RF carriers on select frequency channels (standard DRM broadcast) using a network of recording stations located in different parts of Poland in order to collect data on the HF radio channel. We have been also evaluating the usefulness of this procedure in providing information on the current state of the ionosphere in the refraction region between the transmitter and receivers. When the DRM system becomes more widespread, this method can supplement data that comes from the ionosondes, since it does not require much financial resources and the receivers can be easily scattered over a large area. This paper presents a set of experimental data and its analysis.     

Moderate geomagnetic storms and their ionospheric effects at middle and low latitudes

This paper reports the global response of the mid high and low latitude ionosphere in four longitudinal sectors to two moderate geomagnetic storms that occurred during 2007 (the more intense storms occurred that year). The results obtained during these storms show that the ionospheric effects in general are not moderate in magnitude, showing an important degree of complexity as during intense storms. The outstanding features produced during the storms are significant positive storm effects at mid-high latitudes during the main phase/first part of the recovery, positive effects after the onset of the storm followed by negatives effects at middle latitudes and delayed positive effects during the night-time hours in the trough of the equatorial anomaly (“dusk” effect). Possible physical mechanisms for controlling the morphology of the ionosphere during these events are considered.     

西部地区高校国际交流与合作现状及思考

在经济全球化,教育国际化的大背景下,西部地区高校和西部大开发的强劲东风,积极拓展了教育国际间的交流与合作,有力地推动了西部地区高等教育国际化的进程。但又由于受地域偏远、交通不发达和经济发展缓慢的影响,西部地区高校国际交流与合作和我国东部发展地区相比,在广度和深度方面还有很大的差距,面临着很大的发展空间。     

Space weather center in Japan

Progress in information technology has enabled to collecting data in near real-time. This significantly improves our ability to monitor space weather conditions. We deliver information on near real-time space weather conditions via the internet. We have started two collaborations with space weather users. One is a measurement of geomagnetically induced current (GIC) of power grids in collaboration with a Japanese power company. The other concerns radiation hazards for aircrews. The radiation exposure level for aircrews was been determined by the Japanese government by the end of 2005. The proposed upper limit is 5 mSV a year. We are actively seeking ways to contribute to this subject. Our activities at the Japanese space weather center are reported in this paper.     

On the planetary ionospheric vortex electric fields

The paper presents a physical mechanism of large-scale vortex electric field generation in the ionospheric E- and F-layers. It shows that the planetary-scale, synoptic short-period (from several second to several hours) and fast processes (with propagation velocity higher than 1 km/s) produce a planetary-scale internal vortex electric field. Its value may far exceed that of the dynamo-field generated in the same ionospheric layer by local wind motion. We found, that an ionospheric source of the vortex electric field is spatial inhomogeneity of the geomagnetic field.     

Crew autonomy for deep space exploration: Lessons from the Antarctic Search for Meteorites

Future piloted missions to explore asteroids, Mars, and other targets beyond the Moon will experience strict limitations on communication between vehicles in space and control centers on Earth. These limitations will require crews to operate with greater autonomy than any past space mission has demonstrated. The Antarctic Search for Meteorites (ANSMET) project, which regularly sends small teams of researchers to remote parts of the southern continent, resembles a space mission in many ways but does not rely upon a control center. It provides a useful crew autonomy model for planners of future deep space exploration missions. In contrast to current space missions, ANSMET gives the crew the authority to adjust competing work priorities, task assignments, and daily schedules; allows the crew to be the primary monitor of mission progress; demands greater crew accountability for operational errors; requires the crew to make the most of limited communication bandwidth; adopts systems designed for simple operation and failure recovery; and grants the crew a leading role in the selection and stowage of their equipment.     

Response of the EIA ionosphere to the 7-8 May 2005 geomagnetic storm

In this paper, response of low latitude ionosphere to a moderate geomagnetic storm of 7–8 May 2005 (SSC: 1920 UT on 7 May with Sym-H minimum, ∼−112 nT around 1600 UT on 8 May) has been investigated using the GPS measurements from a near EIA crest region, Rajkot (Geog. 22.29°N, 70.74°E, Geomag.14°), India. We found a decrease in total electron content (TEC) in 12 h after the onset of the storm, an increase during and after 6 h of Sym-H deep minimum with a decrease below its usual-day level on the second day during the recovery phase of the storm. On 8 May, an increase of TEC is observed after sunset and during post-midnight hours (maximum up to 170%) with the formation of ionospheric plasma bubbles followed by a nearly simultaneous onset of scintillations at L-band frequencies following the time of rapid decrease in Sym-H index (−30 nT/h around 1300 UT).