High-Precision Laboratory Measurements Supporting Retrieval of Water Vapor,Gaseous Ammonia,and Aqueous Ammonia Clouds with the Juno Microwave Radiometer (MWR)

The NASA Juno mission includes a six-channel microwave radiometer system (MWR) operating in the 1.3–50 cm wavelength range in order to retrieve abundances of ammonia and water vapor from the microwave signature of Jupiter (see Janssen et al. 2016). In order to plan observations and accurately interpret data from such observations, over 6000 laboratory measurements of the microwave absorption properties of gaseous ammonia, water vapor, and aqueous ammonia solution have been conducted under simulated Jovian conditions using new laboratory systems capable of high-precision measurement under the extreme conditions of the deep atmosphere of Jupiter (up to 100 bars pressure and 505 K temperature). This is one of the most extensive laboratory measurement campaigns ever conducted in support of a microwave remote sensing instrument. New, more precise models for the microwave absorption from these constituents have and are being developed from these measurements. Application of these absorption properties to radiative transfer models for the six wavelengths involved will provide a valuable planning tool for observations, and will also make possible accurate retrievals of the abundance of these constituents during and after observations are conducted.     

Avionics Development and Integration System Methods

This paper describes a set of life cycle methods that were developed in 1980 and 1981 and used in the later phases of the 757/767 airplane programs. They have been used as a framework to establish and guide the introduction of a wide use of similar methods for the future avionics of Boeing's next airplane, the 7J7. The methods were designed to improve communication of the system's requirements, architecture and implementation to a wide group of interested parties ? not just the development engineers but also the users, maintainers, customers and support organizations. A major aspect of these methods is that they were designed to be used for systems in general not just software systems. This paper will describe the background and goals and objectives leading to the need for systems engineering methods, describe the methods and give an example of their use. It will conclude with remarks on steps taken to introduce methods of this type on a wide scale to support the next Boeing airplane.     

Geolocation of frequency-hopping transmitters via satellite

An analysis of satellite-communications terminal geolocation performed by means of interception of ground terminal uplink transmissions in which a number of spaceborne interceptors transpond the frequency band of interest to terrestrial location for processing is presented. Interception regions for prototypical terminals and satellites are calculated and the results are presented parametrically as a function of uplink signal-to-noise ratio (SNR). The optimum angular separation of the interceptor satellites is found, and the effect of nonoptimal separation is discussed, as are the practical limitations involved in implementing this geolocation system     

Reliability of electron density profiles

Deviations from horizontal stratification in the F-region can cause significant errors in electron density profile calculations from ionograms. Such situations exist every day during sunrise and sunset. Angle of arrival measurements and studies of the variation of other F-region parameters indicate that gravity waves are frequently strong enough to produce effects of comparable magnitudes. Ray tracing model studies permit a first order estimate of the resulting errors which are largest for the peak parameters.     

Current legal issues pertaining to space solar power systems

This paper discusses a range of legal issues that need to be considered in planning for a space solar power system. Because objects placed in space are inherently international, the paper primarily looks at international law that affects launching, construction, operation, property rights, the environment, communication and liability. International coordination early in the planning process is urged to make space solar powers systems a reality more speedily.     

A Pre-Landing Assessment of Regolith Properties at the InSight Landing Site

This article discusses relevant physical properties of the regolith at the Mars InSight landing site as understood prior to landing of the spacecraft. InSight will land in the northern lowland plains of Mars, close to the equator, where the regolith is estimated to be \(\geq3\mbox{--}5~\mbox{m}\) thick. These investigations of physical properties have relied on data collected from Mars orbital measurements, previously collected lander and rover data, results of studies of data and samples from Apollo lunar missions, laboratory measurements on regolith simulants, and theoretical studies. The investigations include changes in properties with depth and temperature. Mechanical properties investigated include density, grain-size distribution, cohesion, and angle of internal friction. Thermophysical properties include thermal inertia, surface emissivity and albedo, thermal conductivity and diffusivity, and specific heat. Regolith elastic properties not only include parameters that control seismic wave velocities in the immediate vicinity of the Insight lander but also coupling of the lander and other potential noise sources to the InSight broadband seismometer. The related properties include Poisson’s ratio, P- and S-wave velocities, Young’s modulus, and seismic attenuation. Finally, mass diffusivity was investigated to estimate gas movements in the regolith driven by atmospheric pressure changes. Physical properties presented here are all to some degree speculative. However, they form a basis for interpretation of the early data to be returned from the InSight mission.     

DebrisWatch I: A survey of faint geosynchronous debris

Recent anomalies exhibited by satellites and rocket bodies have highlighted that a population of faint debris exists at geosynchronous (GEO) altitudes, where there are no natural removal mechanisms. Despite previous optical surveys probing to around 10–20 cm in size, regular monitoring of faint sources at GEO is challenging, thus our knowledge remains sparse. It is essential that we continue to explore the faint debris population using large telescopes to better understand the risk posed to active GEO satellites. To this end, we present photometric results from a survey of the GEO region carried out with the 2.54 m Isaac Newton Telescope in La Palma, Canary Islands. We probe to 21st visual magnitude (around 10 cm, assuming Lambertian spheres with an albedo of 0.1), uncovering 129 orbital tracks with GEO-like motion across the eight nights of dark-grey time comprising the survey. The faint end of our brightness distribution continues to rise until the sensitivity limit of the sensor is reached, suggesting that the modal brightness could be even fainter. We uncover a number of faint, uncatalogued objects that show photometric signatures of rapid tumbling, many of which straddle the limiting magnitude of our survey over the course of a single exposure, posing a complex issue when estimating object size. This work presents the first instalment of DebrisWatch, an ongoing collaboration between the University of Warwick and the Defence Science and Technology Laboratory (UK) investigating the faint population of GEO debris.     

Characteristic γ- and X-radiation in the planetary system

Conclusions Passive observation of the naturally occurring γ-ray and X-ray from the planets is potentially an important technique for determining their gross chemical composition and on the basis of natural γ-radiation determining if the planetary surface is composed of differential material. If the planet is not covered by a thick atmosphere then it is possible to map the distribution of the most abundant elements on a scale of spatial resolution that is of the order of the altitude at which the observations are made. Initial observations carried out from lunar orbit have shown that the flux levels are approximately as expected and that the lunar surface is not characterized by any widespread distribution of acidic rocks in the region observed by the Luna 10 spacecraft.