Astronomy Through Practical Investigations

[Trinidad Baltzell]

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In practical situations, one often generates a beam by superposition of two or more light beams. The beam generated by superposition displays, in general, different spectral properties than do the original beams. However, there are some optical beams, called cross-spectrally pure beams, which can generate a light beam of identical spectral distribution on superposition. The relationship between cross-spectral purity and spatial coherence has been the subject of investigations for some time. Recently, a concept of so-called statistical similarity has been introduced which provides a new way to elucidate complete spatial coherence. In this Letter, we discuss some implications of statistical similarity of an optical field on its cross-spectral purity.

Abstract: Mid-infrared spectra of galaxies contain thermal emission from warm dust and broad emission lines from transiently heated polycyclic aromatic hydrocarbon molecules. Low and moderate spectral resolution observations are sensitive to star-formation rates, radiation environments, and heating by active galactic nuclei. Multiple detector technologies and spectrometer architectures are viable for mid-infrared wavelengths. This talk will focus on kinetic inductance detector development and high mapping speed, low resolution spectral imaging enabled by a compact linear-variable filter spectrometer configuration in the range of approximately 10 to 30 microns and longer.

Abstract: A submillimeter spectrometer for SOFIA will be described. The spectrometer will optimize sensitivity in the 500 - 600 GHz frequency region. The maximization of sensitivity will employ methods previously used on the Herschel HIFI instrument. Additionally, new state-of-the-art detectors will be designed and built which have minimum noise temperatures. The instrument will be described, and the instrument response curve will be presented. Comparisons of the sensitivity to HIFI will also be discussed. Potential science measurements will be presented.

Abstract: We will review the technology for high resolution heterodyne spectrometers for the Terahertz spectral range under the boundary conditions set by the airborne observatory SOFIA. The talk will discuss the possibilities and limitations of the optical system, possible detector and local oscillator schemes as well as the challenges of intermediate frequency processing and spectrometer backends.

Abstract: I present a summary of the First SOFIA Instrument Roadmap Workshop. First, I outline the science cases presented. Second, I discuss the instrumental capability needed to deliver the potential science. Next, I discuss some of the gaps in capability identified in the first workshop. Finally, I discuss the process moving forward to produce the Instrument Roadmap for NASA.

Abstract: I discuss some potential recommendations that may form part of the SOFIA Instrument Roadmap. First, I discuss steps for a "science-driven" development process that first identifies the key science, then specifies the capabilities necessary to achieve that science, and then solicits the community to build an instrument with these capabilities. Next, I discuss two options for the phasing of instruments, one more sequential and the other more parallel.

Abstract: Further leaps in terahertz (THz) astronomy demand new detector materials and devices reaching the fundamental detection limit. Superconducting hot-electron bolometer (S-HEB) mixers form the baseline for modern astronomical receivers above 1 THz. In these, the wave beating between the Local Oscillator (LO) and the THz signal causes temperature oscillations in a metal around the transition temperature, at the Intermediate Frequency (IF), enabling read-out through changes in electrical resistance R (resistive read-out) as long as the temperature can follow the signal modulation. Despite huge efforts, the instantaneous bandwidth in practical niobium nitride (NbN)-based S-HEB mixers does not exceed 4-5GHz, limited by the electron temperature relaxation rates. Beyond superconducting materials, charge-neutral graphene has been discussed as an ideal platform for terahertz bolometric direct detectors due to its small heat capacity and weak electron-phonon coupling. Prior to this work, the absence of large-area graphene homogeneously doped to Dirac point had hindered any prospects for graphene-based practical detectors in astronomy and other sensing applications. Furthermore, a negligible temperature dependent resistance of graphene has kept this approach as not acceptable for bolometric mixers where voltage read-out is required.

We have investigated epitaxial graphene grown on silicon carbide (epigraphene) that is doped to the Dirac point with a high uniformity across the wafer. With the resistance dominated by quantum localization, and thermal relaxation of carriers governed by electron diffusion, we demonstrate an epigraphene bolometric terahertz mixer with a gain bandwidth (presently) of 9 GHz (relaxation time 20 ps) and a mixer noise temperature of 475 K. We conclude that with the present quality of graphene, optimization of the device layout will result in a mixer noise temperature as low as 36 K and a gain bandwidth exceeding 20 GHz, with a Local Oscillator power of Abstract: One innovative approach to enabling SOFIA instrument development is the concept of designing and potentially manufacturing a 'Common Dewar', which would be usable by a wide range of Astronomical experiments, but would fulfill SOFIA requirements (e.g. airworthiness, EMC/EMI and flange interface tolerances). One investigation of this concept was the Standard New Astronomy Cryostat for SOFIA (SNACS) While partially used to enable adoption of cryocoolers onboard SOFIA, the system was also used as a testbed for a potential common dewar concept, featuring a cryostat with a 4K Optical bench and optional support for additional cooling stages (such as an ADR). Other approaches to a Common Dewar could also include development of a common dewar design or utilization of already-approved cryostats from retired instruments in new SOFIA instruments, technology demonstrations or testbeds. This talk will examine these approaches, the SNACS design study and potential future applications of a Common Dewar concept for SOFIA instrument development.

Abstract: We will provide an introduction and overview of Transition Edge Sensors (TES) used for far-infrared astronomy and beyond. Important properties of TES making them suitable for future instrumentation will be highlighted together with an outlook on potential suborbital and space-based instruments and missions.

A lot of people are highly concerned that a malevolent AI or insane human will, in the near future, set out to destroy humanity. If such an entity wanted to be absolutely sure they would succeed, what method would they use? Nuclear war? Pandemics?

The nanomachinery builds diamondoid bacteria, that replicate with solar power and atmospheric CHON, maybe aggregate into some miniature rockets or jets so they can ride the jetstream to spread across the Earth's atmosphere, get into human bloodstreams and hide, strike on a timer.

I was interested to know more. What is diamondoid bacteria? How far along is molecular nanotech research? What are the challenges that we (or an AI) will need to overcome to create this technology?

It is my hope that by trying to answer these questions, I can give you a taste of what nanoscale research actually looks like. It ended up being the tale of a group of scientists who had a dream of revolutionary nanotechnology, and tried to answer the difficult question: How do I actually build that?

However, Drexlers actual designs of how a molecular assembler would be built have been looked on with extreme skepticism by the wider scientific community. And while some of the criticisms have been unfair (such as accusations of pseudoscience), there are undeniably extreme engineering challenges. The laws of physics are felt very differently at different scales, presenting obstacles that have never been encountered before in the history of manufacturing, and indeed may turn out to be entirely insurmountable in practice. How would you actually make such a device?

This is all a little chaotic. What if we wanted to do something more controlled? The goal of mechanosynthesis is to precisely control the reactive elements we wish to put together by using mechanical force to precisely position them together. In this way, the hope is that extremely complex structures could be assembled atom by atom or molecule by molecule.

Diamondoid materials also may include any stiff covalent solid that is similar to diamond in strength, chemical inertness, or other important material properties, and possesses a dense three-dimensional network of bonds. Examples of such materials are carbon nanotubes (illustrated at right) or fullerenes, several strong covalent ceramics such as silicon carbide, silicon nitride, and boron nitride, and a few very stiff ionic ceramics such as sapphire (monocrystalline aluminum oxide) that can be covalently bonded to pure covalent structures such as diamond.

The plan was to engage in both theoretical and experimental research to develop nanotech in several stages. Step 1 was to achieve working prototypes of diamond mechanosynthesis. Step 2 was to build on this to actually assemble complex molecular structures in a programmable mechanical manner. Step 3 was to find a way to parallelize the process, so that huge amounts of assembly could be done at once. Step 4 was to use that assembly to build a nanofactory, capable of building a huge number of things, including a copy of itself. The proposed timeline for this project is shown below:

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