Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI): Instrument Design and Calibration

The Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument was built for launch and operation on the NASA Ionospheric Connection Explorer (ICON) mission. The instrument was designed to measure thermospheric horizontal wind velocity profiles and thermospheric temperature in altitude regions between 90 km and 300 km, during day and night. For the wind measurements it uses two perpendicular fields of view pointed at the Earth’s limb, observing the Doppler shift of the atomic oxygen red and green lines at 630.0 nm and 557.7 nm wavelength. The wavelength shift is measured using field-widened, temperature compensated Doppler Asymmetric Spatial Heterodyne (DASH) spectrometers, employing low order échelle gratings operating at two different orders for the different atmospheric lines. The temperature measurement is accomplished by a multichannel photometric measurement of the spectral shape of the molecular oxygen A-band around 762 nm wavelength. For each field of view, the signals of the two oxygen lines and the A-band are detected on different regions of a single, cooled, frame transfer charge coupled device (CCD) detector. On-board calibration sources are used to periodically quantify thermal drifts, simultaneously with observing the atmosphere. The MIGHTI requirements, the resulting instrument design and the calibration are described.     

Irregular Satellites in the Context of Planet Formation

All four giant planets in the solar system possess irregular satellites, characterized by large, highly eccentric and/or highly inclined orbits. These bodies were likely captured from heliocentric orbit, probably in association with planet formation itself. Enabled by the use of large-format digital imagers on ground-based telescopes, new observational work has dramatically increased the known populations of irregular satellites, with 74 discoveries in the last few years. A new perspective on the irregular satellite systems is beginning to emerge.We find that the number of irregular satellites measured to a given diameter is approximately constant from planet to planet. This is surprising, given the radically different formation scenarios envisioned for the gas giants Jupiter and Saturn compared to the (much less massive and compositionally distinct) ice giants Uranus and Neptune. We discuss the new results on the irregular satellites and show how these objects might be used to discriminate amongst models of giant planet formation.     

Overview and status of a mirror fusion propulsion system design study

The main goal of this paper is to describe and emphasize the important discoveries made since 1986 in the engineering design of space fusion propulsion plants.

Among the important discoveries are four fundamental design principles (DPs) which should be used when adapting candidate Earth-based fusion-electric power plants to propulsion in space.

1. DP1. Maximize direct access to space for waste radiation.

2. DP2. Operate components as passive radiators whenever possible.

3. DP3. Optimize the plasma characteristics for best specific jet power

4. DP4. Optimize mission capability versus lifetime-mass-to-orbit (LMTO).

Another discovery is a design philosophy called IDEAs (Integrated Design Environment Algorithms) which is a tool for discovering new fundamental design principles.

These discoveries allowed us to adapt, and then to optimize, an earth-based fusion-electric magnetic-mirror-fusion reactor concept for propulsion in space. The resulting design is called the Mirror Fusion Propulsion System (MFPS); and its design status is reviewed.

This work can be used as a general road map for others attempting to convert earth-based designs to propulsion in space. It also has applicability to matter-antimatter propulsion systems engineering.     

Comparison of three soil-like substrate production techniques for a bioregenerative life support system

It is very important to recycle the inedible biomass of higher plants to improve the closure of bioregenerative life support system (BLSS). Processing candidate higher plant residues into the soil-like substrate (SLS) as the plant growth medium is a promising way to achieve. In this study, three different processing techniques of SLSs, using residues of wheat and rice as feedstock, were compared. As for the first traditional technique, SLS1 was obtained by successive conversion of wheat straw by oyster mushrooms and worms. In the other two methods, SLSs were produced with aerobic fermentation (SLS2) or anaerobic fermentation (SLS3) followed by worm conversion. The changes in SLS cellulose, lignin, available elements and pH were measured during the production processes. The maturity was evaluated by the value of C/N. The fertilities were compared in terms of available elements contents and lettuce productivities. The results indicated that the second technique was optimal, whose process cycle was 30 days less than that of SLS1. The total cellulose and lignin degradation of SLS2, achieved 98.6% and 93.1% during the 93-days-processing, and the lettuce productivity reached 12.0 g m⁻² day⁻¹.     

How far – if at all – should the USA cooperate with China in space?

China has engaged in a steady, long-standing effort to build and strengthen its space capabilities, achieving progressively more ambitious milestones and staking its claim as a major space power. It is also increasingly engaging in cooperative efforts. A number of issues must be weighed, however, before the USA should consider any collaboration with it. These include the essentially military nature of China’s space program, the fact that China’s intentions in space and decision-making process are far from ‘transparent’, and the way it uses its space activities to pursue foreign policy goals. While the latter could be useful in, e.g., reducing tensions on the Korean peninsular through a space-services-for-giving-up-missiles tradeoff, and while there is scope for collaboration in space science missions, there are no compelling reasons for the USA to pursue cooperation in human spaceflight with China.     

Error Reduction in HF Loop DF Systems

Techniques for reducing bearing errors in vertical loop HF direction finders for ionospherically propagated signals were evaluated in a dual-channel system. A main channel provides a bearing display from the output of a rotating loop; an auxiliary channel unblanks the bearing ng display when propagation conditions are favorable for minimum bearing error. Circuitry to provide optimum unblanking for a wide variety of signal and fade conditions is described. The results of an operational evaluation are presented and show that a large majority of the unblanked bearings can be restricted to ±15° of the great-circle bearing with average bearing errors of 10° or less. Operational comparison with a contemporary system shows that the dual-channel system performance is superior with a 2 to 1 reduction ion in bearing spreads, standard deviations, and RMS error.     

一种节油的柔性变形机翼

最近美国柔性系统公司在缩比复合材料公司的"白色骑士"飞行试验台上,完成了一项"自适应柔性机翼"技术的飞行试验。这项研制工作得到了美国空军研究实验室的支持,此前已经成功地完成了风洞试验。这种采用层流翼型的自适应柔性机翼被垂直地安装在"白色骑士"飞机的挂架上,分别在8000米和13000米高度上进行了7次飞行试验,累计飞行20小时。装在飞机尾部下方的摄像机可以使机组人员检验试     

The Mercury Dual Imaging System on the MESSENGER Spacecraft

The Mercury Dual Imaging System (MDIS) on the MESSENGER spacecraft will provide critical measurements tracing Mercury’s origin and evolution. MDIS consists of a monochrome narrow-angle camera (NAC) and a multispectral wide-angle camera (WAC). The NAC is a 1.5° field-of-view (FOV) off-axis reflector, coaligned with the WAC, a four-element refractor with a 10.5° FOV and 12-color filter wheel. The focal plane electronics of each camera are identical and use a 1,024×1,024 Atmel (Thomson) TH7888A charge-coupled device detector. Only one camera operates at a time, allowing them to share a common set of control electronics. The NAC and the WAC are mounted on a pivoting platform that provides a 90° field-of-regard, extending 40° sunward and 50° anti-sunward from the spacecraft +Z-axis—the boresight direction of most of MESSENGER’s instruments. Onboard data compression provides capabilities for pixel binning, remapping of 12-bit data into 8 bits, and lossless or lossy compression. MDIS will acquire four main data sets at Mercury during three flybys and the two-Mercury-solar-day nominal mission: a monochrome global image mosaic at near-zero emission angles and moderate incidence angles, a stereo-complement map at off-nadir geometry and near-identical lighting, multicolor images at low incidence angles, and targeted high-resolution images of key surface features. These data will be used to construct a global image base map, a digital terrain model, global maps of color properties, and mosaics of high-resolution image strips. Analysis of these data will provide information on Mercury’s impact history, tectonic processes, the composition and emplacement history of volcanic materials, and the thickness distribution and compositional variations of crustal materials. This paper summarizes MDIS’s science objectives and technical design, including the common payload design of the MDIS data processing units, as well as detailed results from ground and early flight calibrations and plans for Mercury image products to be generated from MDIS data.     

Law aboard the space station

For over two decades, multilateral treaties have governed the spaceborne activities of nations in a variety of situations. In recent years, however, it has been apparent that a legal vacuum exists concerning the activities of individual citizens who are sent into space by the spacefaring nations. Few laws exist which are specifically intended to regulate private individuals and entities in space. This situation has led to uncertainty for potential participants in NASA's international Space Station programme. Moreover, it now appears that the Intergovernmental Agreement concerning the Space Station may not solve the problem.