although the LEO constellation has dynamic satellite network topology, the topology changes are predictable and periodic. Based on the characteristics above, a new simple change adaptive routing algorithm (SCARA) is proposed for satellite IP networks. SCARA uses simple rules to decide the next hop. The rules are 1) using only two possible directions to reduce the routing path; 2) assigning high...

A common challenge in developing small-satellite-based Earth-observation (EO) missions is getting the data to the ground. Typically, most satellites download data via space-to-ground radio-frequency (RF) links, communicating directly with fixed ground stations as the satellites fly within range. For many next-generation EO missions, such as hyperspectral imaging or SAR missions, the volume of d...

We present new kinematic results for a sample of 387 stars located in and around the Milky Way satellite dwarf spheroidal galaxy Leo I. These spectra were obtained with the Hectochelle multi-object echelle spectrograph on the MMT, and cover the MgI/Mgb lines at about 5200Å. Based on 297 repeat measurements of 108 stars, we estimate the mean velocity error (1σ) of our sample to be 2.4 km/s, with...

We address the problem of interference as related to Satellite Personal Communication Networks (S-PCNs). Basic low Earth orbit (LEO) constellation is considered. The paper uses combined adaptive antenna arrays and adaptive filtering technique. This hybrid linear adaptive technique provides improved performance eliminating interference, particularly uncorrelated signals residing in the antenna s...

This paper presents a coded modulation scheme based on M-ary orthogonal modulation by means of Walsh–Hadamard (WH) sequences, suitable for low-earth-orbit (LEO) direct sequence/code division multiple access (DS/CDMA) satellite communication systems. Based on the IS-95 scheme, we consider Reed–Solomon (RS)-coded M-ary orthogonal modulation with error or erasures decoding, which presents good per...

although the LEO constellation has dynamic satellite network topology, the topology changes are predictable and periodic. Based on the characteristics above, a new simple change adaptive routing algorithm (SCARA) is proposed for satellite IP networks. SCARA uses simple rules to decide the next hop. The rules are 1) using only two possible directions to reduce the routing path; 2) assigning high...

GEO Satellite imagery is an important tool and can be used to estimate rainfall during the thunderstorms and hurricanes for flash flood warnings in real time. However, for the GEO satellite is located higher than normal LEO satellite, the spatial resolution images are lower. Therefore, in order to obtain an image with enough resolution, some methods are to be implemented in GEO satellite observ...

This paper focuses on the radio resource management in low earth orbit-mobile satellite systems (LEOMSSs) based on a time division multiple access (TDMA) air interface. A novel demand–assignment medium access control (MAC) protocol, named DRAMAþ (dynamic resource assignment multiple access}enhanced version), is proposed, where voice and Web traffic sources obtain transmission slots through requ...