Biospheres and solar system exploration

The implications of biosphere technology is briefly examined. The exploration status and prospects of each world in the solar system is briefly reviewed, including the asteroid belt, the moon, and comets. Five program elements are listed as particularly critical for future interplanetary operations during the coming extraterrestrial century. They include the following: (1) a highway to Space (earth orbits); (2) Orbital Spaceports to support spacecraft assembly, storage, repair, maintenance, refueling, launch, and recovery; (3) a Bridge Between Worlds to transport cargo and crews to the moon and beyond to Mars; (4) Prospecting and Resource Utilization Systems to map and characterize the resources of planets, moons, and asteroids; and (5) Closed Ecology Biospheres. The progress in these five field is reviewed

Structural techniques in descriptive complexity

In 2017, Abramsky, Dawar, and Wang published a paper which gave a comonadic characterisation of pebble games, tree-width, and k-variable logic, a key trio of related concepts in Finite Model Theory. In 2018, Abramsky and Shah expanded upon this to give an analogous comonadic characterisation of Ehrenfeucht Fraisse games, tree-depth, and bounded quantifier rank logic. A key feature of these papers is the connection between two previously distinct subfields of logic in computer science; Categorical Semantics, and Finite Model Theory. This thesis applies the ideas and techniques in these papers to give a categorical account of some cornerstone results of Finite Model Theory, including Rossman’s Equirank Homomorphism Preservation Theorem, Courcelle’s Theorem (on the model-checking properties of structures of bounded tree-width), and Gaifman’s Locality Theorem

Electronic countermeasures applied to passive radar

Passive Radar (PR) is a form of bistatic radar that utilises existing transmitter infrastructure such as FM radio, digital audio and video broadcasts (DAB and DVB-T/T2), cellular base station transmitters, and satellite-borne illuminators like DVB-S instead of a dedicated radar transmitter. Extensive research into PR has been performed over the last two decades across various industries with the technology maturing to a point where it is becoming commercially viable. Nevertheless, despite the abundance of PR literature, there is a scarcity of open literature pertaining to electronic countermeasures (ECM) applied to PR. This research makes the novel contribution of a comprehensive exploration and validation of various ECM techniques and their effectiveness when applied to PR. Extensive research has been conducted to assess the inherent properties of the lluminators of Opportunity to identify their possible weaknesses for the purpose of applying targeted ECM. Similarly, potential jamming signals have also been researched to evaluate their effectiveness as bespoke ECM signals. Whilst different types of PR exist, this thesis focuses specifically on ECM applied to FM radio and DVB-T2 based PR. The results show noise jamming to be effective against FM radio based PR where jamming can be achieved with relatively low jamming power. A waveform study is performed to determine the optimal jamming waveform for an FM radio based PR. The importance of an effective direct signal interference (DSI) canceller is also shown as a means of suppressing the jamming signal. A basic overview of counter-ECM (ECCM) is discussed to counter potential jamming of FM based PR. The two main processing techniques for DVB-T2 based PR, mismatched and inverse filtering, have been investigated and their performance in the presence of jamming evaluated. The deterministic components of the DVB-T2 waveform are shown to be an effective form of attack for both mismatched filtering and inverse filtering techniques. Basic ECCM is also presented to counter potential pilot attacks on DVB-T2 based PR. Using measured data from a PR demonstrator, the application and effectiveness of each jamming technique is clearly demonstrated, evaluated and quantified

Lecture capture using large interactive display systems

There are various software technologies that allow capture and redelivery of lectures. Most of these technologies however rely on the use of proprietary software, often requiring extra efforts from the lecturer in terms of the initial preparation of the lecture material, or in editing and annotating after the lecture to make the material suitable for the students. To review the material students then require access to the proprietary software. This paper describes a system for the lightweight capture of lecture presentations, based on the use of a low-cost large interactive display surface, together with standard Microsoft PowerPoint™ presentation software. The captured version of the presentation includes the original lecture slides, graphical annotations made by the lecturer during the lecture, and the audio recording of the lecture; all saved as a PowerPoint file. In addition, the system adds some annotations and index slides to allow quick and easy access to different segments of the presentation. Presentations can be replayed in part or in full as required, preserving all of the content of the live lecture

Recirculating 1-K-Pot for Pulse-Tube Cryostats

A paper describes a 1-K-pot that works with a commercial pulse tube cooler for astrophysics instrumentation testbeds that require temperatures <1.7 K. Pumped liquid helium-4 cryostats were commonly used to achieve this temperature. However, liquid helium-4 cryostats are being replaced with cryostats using pulse tube coolers. The closed-cycle 1K-pot system for the pulse tube cooler requires a heat exchanger on the pulse tube, a flow restriction, pump-out line, and pump system that recirculates helium-4. The heat exchanger precools and liquefies helium- 4 gas at the 2.5 to 3.5 K pulse tube cold head. This closed-cycle 1-K-pot system was designed to work with commercially available laboratory pulse tube coolers. It was built using common laboratory equipment such as stainless steel tubing and a mechanical pump. The system is self-contained and requires only common wall power to operate. The lift of 15 mW at 1.1 K and base temperature of 0.97 K are provided continuously. The system can be scaled to higher heat lifts of .30 to 50 mW if desired. Ground-based telescopes could use this innovation to improve the efficiency of existing cry