Suitable Strategies for In-plane Orbit Acquisition using Micro-thrusters

The deviations in the injection orbital parameters, resulting from launcher dispersions, need to be corrected through a set of acquisition maneuvers to achieve the desired nominal parameters. When multiple satellites are injected into a single orbital plane, as a part of constellation establishment, they have to positioned in the plane with appropriate semi-major axis ‘a’ and mean anomaly ‘M’. In this paper, three strategies are studied for achieving orbit acquisition. The first strategy is by deriving an analogy to the Linear Quadratic Regulator (LQR). The state dynamics and the control law are of the form X&= AX + BU and U = −KX . The feedback gain K is calculated by minimizing the cost function. Under this strategy the thrust (N) and velocity increment ( ÄV ) are functions of time and only the matrix K needs to be up-linked. Any revision in the current or the target states, will then lead to a simple re-calculation of K and up-linking them. The second strategy assumes that ÄV is same for each maneuver and calculates the number of maneuvers and the ÄV required for each maneuver. If the maneuvers are stopped for reasons like orbit assessment, and thruster performance evaluation, the strategy can be restarted easily without having any penalty on the overall ÄV. Besides these two strategies, a third strategy based on the application of Fuzzy Modified Potential Function is also studied for autonomous orbit acquisition with constraints in the path. By adding Fuzzy logic to the potential function it is shown that, maneuvers can be changed gradually ahead of the constraints. Onboard implementation related aspects are also briefly addressed for all the strategies

First Record of Marine Dinoflagellate, Alexandrium Tamutum (Dinophyceae) from Malaysia

Several species of dinoflagellates in the genus Alexandrium are known to be toxic, and have been associated with paralytic shellfish poisoning (PSP) in Malaysia. These Alexandrium species showed high morphological similarity among the toxic and non-toxic species, and detailed observation of the thecal plate’s arrangement is required for precise species identification. Co-occurrence of the toxic and non-toxic species has complicated the plankton monitoring of PSP. In this study, a clone of Alexandrium species was established from plankton samples collected from Kota Belud, Sabah. The specimen was observed under epi-fluorescence microscope, and nucleotide sequences of the nuclear-encoded ribosomal RNA gene obtained. Morphologically, the clone showed relatively wide and large sixth precingular plate (6´´) compared to that of A. minutum. The sulcal posterior plate (Sp) is similar to that of A. minutum, which is wider than long. The first apical plate (1´) is irregularly rhomboidal with a small ventral pore (vp) present on its right margin. The morphological characters resembled to the species description of A. tamutum. Phylogenetic analysis of the ITS rDNA region also revealed a monophyly of this clone with other strains of A. tamutum, and separating them from the A. minutum clade. Species-specific sequence signatures of A. tamutum were obtained in silico, which could be as potential oligonucleotide probe regions for species detection by using molecular tool. This represents the first report of A. tamutum found in Malaysian waters

Merlion L & S Band System

Under the MERLION project name, Nanyang Technological University of Singapore has teamed up with Surrey Satellite Technology Ltd. of the UK and developed a sophisticated communication payload on the UoSAT-12 mini-satellite which was launched recently. The MERLION payload combines an analogue and digital regenerative transponder, with L-band uplink and S-band downlink. The transponder can be configured in-orbit for a variety of functions and experiments, and carries dual signal processors. The digital uplink comprises a frequency agile L-band receiver, and 9600bps FSK and IMbps BPSK demodulators. The frequency agile digital S-band downlink is intended for high speed data transfer and will be employed to perform a variety of communication experiments. It is also capable of low bit rate spread spectrum communications, together with convolutional coding options to investigate its performance in the highly dynamic environment of LEO. The downlink can be configured to perform link characterisation at these frequencies. In conjunction with the 80386EX based On-Board-Computers, the digital uplink and downlink system can be configured into a high rate Store-and-Forward transponder. This paper would introduce the basic Medion architecture and design considerations, to realise the above functionality within the scope of a low cost mission

A bloom of Karlodinium australe (Gymnodiniales, Dinophyceae) associated with mass mortality of cage-cultured fishes in West Johor Strait, Malaysia

A recent (February 2014) mass mortality of fishes was observed in the cage-farming region of the West Johor Strait of Malaysia, involving over four different species of cultured fishes, numbering ∼50,000 fish. A field investigation at six stations along the West Johor Strait collected water samples and examined for the presence of harmful species. Dead fishes were collected for necropsy. The phytoplankton composition was dominated by a species of Karlodinium, at a considerably high cell concentration (0.31–2.34 × 106 cells l−1), and constituting 68.8–98.6% of the phytoplankton relative abundance at all stations. Detailed morphological assessment by light and scanning electron microscopy revealed that the species was Karlodinium australe de Salas, Bolch and Hallegraeff. This was supported by molecular evidence of the nuclear encoded large subunit ribosomal gene (LSU rDNA) and the second internal transcribed spacer (ITS2) via single-cell PCR. The sequences of LSU rDNA yielded 3.6–4.0% divergence when compared to the sister taxon, K. armiger; and >6.5% when compared to other Karlodinium species. Fish necropsy showed symptoms similar to those affected by karlotoxin ichthyotoxins. This is the first report of a mass mortality of cage-cultured and wild fishes attributed to the unarmored dinoflagellate K. australe

Ground system for satellite engineering

The main objective of this academic research project is the design and development of a novel software architecture based on distributed computing technologies for aerospace flight control and test systems which typically demand a secure, robust, flexible and scalable network environment for their mission critical operations. The need for distributed operations and flexible inter-operability between a heterogeneous mixture of hardware/software systems via objectoriented connectivity leads to this Service Oriented Architecture (SOA) design concept for the software architecture in NTU’s satellite groundstation. A typical application of this satellite ground control system would be the support for mission control and operation of the X-Sat micro-satellite project, such as telemetry, tracking and commanding applications.RG 01/0

Microwave integrated circuits: design, fabrication and testing

This report covers a thorough study of the design, fabrication and testing of MIC. The main application area identified is the design and development of a low cost DBS receiver.RP 22/8

Microwave integrated circuits : design, fabrication & testing

This is an addendum to Appendix (2) of the Final Report RP 22/83.RP 22/8

Telecommunication and information techniques and systems

This report consists of two parts :- Part 1: Millimeter-wave wireless antennas - FDTD method of analysis and design. Part 2: Analysis and design of conical pattern patch antennas for micro-satellite.RGM 4/9

Integrated millimeter wave antenna/receiver frontend module for wireless LAN applications

The project designed and developed low cost transceiver frontend modules for a wireless LAN system operating in the millimeter wave band - the frequency of 35 GHz in the Ka-band was chosen.RG 30/9