NISCAIR Online Periodicals Repository Collection: IJRSP Vol.36(5) [October 2007]

GPS radio occultation on-board the OCEANSAT-2 mission: An Indian (ISRO) – Italian (ASI) collaboration

Fri, 28 Sep 2007 22:58:59 GMT

Title: GPS radio occultation on-board the OCEANSAT-2 mission: An Indian (ISRO) – Italian (ASI) collaboration

Authors: Perona, Giovanni; Notarpietro, Riccardo; Gabella, Marco

Abstract: In the first quarter of 2008, the Indian satellite OCEANSAT-2 will be launched. The Italian Space Agency (ASI) signed a Memorandum of Understandings with the Indian Space Research Organization (ISRO) in which it is agreed to put on-board the OCEANSAT-2 satellite the Italian GNSS receiver devoted to Radio Occultation (ROSA–Radio Occultation Sounder of the Atmosphere). The ROSA receiver has been developed with a new-concept hardware configuration with respect to that normally characterizing a GNSS receiver: it will track the GPS “occulted” signal both just before its setting and just after its rising from the local horizon using an open loop technique, and it will automatically switch from (or to) the standard closed loop approach when the signal crosses higher atmospheric regions. Observations from ROSA will be downloaded both to the Indian and the Italian receiving stations where they will be processed by the ROSA Ground Segment, developed by Italian universities and research centres. In particular, the first version of the processing software will be integrated in a ground segment installed in Matera (Italy) and mirrored at Hyderabad (India). Its second version will be installed in a distributed ground segment implemented by connecting, on a web-based GRID, hardware and software infrastructures installed at the research centres and universities involved in its development.

Page(s): 386-393

Remote sensing of radio ducts using wind profilers

Fri, 28 Sep 2007 22:58:59 GMT

Title: Remote sensing of radio ducts using wind profilers

Authors: Sengupta, N; Glover, I A

Abstract: A case study is presented of refractivity gradient height-profile retrieval using a 915 MHz wind profiler operated by the UK Meteorological Office at Camborne, UK. The retrieved gradient compares well with that obtained from concurrent radiosonde data gathered at the same location, thus demonstrating the potential of such profilers for the investigation of duct dynamics and the collection of unbiased duct statistics.

Page(s): 383-385

Estimation of cross-polarization due to rain over some stations in India

Fri, 28 Sep 2007 22:58:59 GMT

Title: Estimation of cross-polarization due to rain over some stations in India

Authors: Jaiswal, R Sen; Geetha, P; Uma, S

Abstract: In this paper an attempt has been made to compute cross-polarization of millimeter waves in the 30-35 GHz frequency range due to rain. Laws and Parson’s drop size distributions for oblate spheroid drops at 20ºC ITU-R (2002) model has been used to predict cross-polarization discrimination (XPD) for circular polarization. The study includes a number of earth stations in India, namely, Ahmedabad, Calcutta, Delhi, Gangtok and Jodhpur. Variations of co-polar attenuation with XPD have been shown. Cumulative time distribution of XPD has also been presented. The study reveals that cross-polarization depends on frequency, co-polar attenuation and rainfall rate. Comparison with measurement does not show good agreement although the two show the same trend. Extensive work on cross-polarization is required in the millimeter wave frequency range over a large number of earth stations in India using different drop size distributions and different polarizations.

Page(s): 379-382

Cloud attenuation and cloud noise temperature over some Indian eastern stations for satellite communication

Fri, 28 Sep 2007 22:58:59 GMT

Title: Cloud attenuation and cloud noise temperature over some Indian eastern stations for satellite communication

Authors: Kumar, Anil; Sarkar, S K

Abstract: In this paper, cloud characteristics in relation to radio wave propagation over some selected locations in different geographical region in eastern India have been presented. It is seen that low cloud occurrence over Patna, Bhubaneswar and Ranchi is quite significant. The performance of radio systems deteriorates due to cloud attenuation as well as due to cloud noise temperature. Based on the cloud attenuation results, the total atmospheric noise temperature including the noise contribution from cloud for different months during different times for different cloud thicknesses at 10 GHz, 18 GHz, 32 GHz, 44 GHz and 70 GHz has been determined for the aforesaid stations. The results, presented here are useful to design future earth- space communication links over these aforesaid locations in India.

Page(s): 375-378