I’ve skimmed through the Fall 2008 American Geophysical Union abstracts for those that provide enough information on proposed future missions to be interesting standalone documents. (Often the abstracts for future missions discuss what will be talked about rather than providing details.) You can peruse the entire planetary portion of the meeting at: http://www.agu.org/cgi-bin/sessions5?meeting=fm08&sec=P. Presentation numbers for each of the abstracts is given so you can look up authors, etc., from the full abstract.
I will be attending the conference, but for my primary field, the remote sensing of vegetation structure. I’ll attend as many of the planetary sessions as possible, but this is a huge conference and only a tiny fraction of presentations in any field can be attended.
TI: Nuclear Polar VALOR: An ASRG-Enabled Venus Balloon Mission Concept
AB: In situ exploration of Venus is expected to answer high priority science questions about the planet's origin, evolution, chemistry, and dynamics as identified in the NRC Decadal Survey and in the VEXAG White Paper. Furthermore, exploration of the polar regions of Venus is key to understanding its climate and global circulation, as well as providing insight into the circulation, chemistry, and climatological processes on Earth. In this paper we discuss our proposed Nuclear Polar VALOR mission, which would target one of the polar regions of Venus, while building on design heritage from the Discovery class VALOR concept, proposed in 2004 and 2006. Riding the strong zonal winds at 55 km altitude and drifting poleward from mid-latitude this balloon-borne aerial science station (aerostat) would circumnavigate the planet multiple times over its one- month operation, extensively investigating polar dynamics, meteorology, and chemistry. Rising and descending over 1 km altitude in planetary waves - similar to the two VEGA balloons in 1985 - onboard instrumentation would accurately and constantly sample and measure other meteorological and chemical parameters, such as atmospheric temperature and pressure, cloud particle sizes and their local column abundances, the vertical wind component, and the chemical composition of cloud-forming trace gases. As well, when viewed with terrestrial radio telescopes on the Earth-facing side of Venus, both zonal and meridional winds would be measured to high accuracy (better than 10 cm/sec averaged over an hour). Due to three factors: the lack of sunlight near the poles; severe limitations on the floating mass-fraction available for a power source; and the science requirements for intensive and continuous measurements of the balloon's environment and movement, a long-duration polar balloon mission would require a long-lived internal power source in a relatively lightweight package. For our concept we assumed an Advanced Stirling Radioisotope Generator (ASRG). In return, this mission would provide two orders of magnitude more science data than expected from the original battery-powered VALOR concept, and could reduce measurement uncertainties by a factor of five. In addition to the science return, the secondary objective of this proposed mission would be to space qualify ASRGs through all mission phases and in various operating environments. Lifetime testing would be demonstrated using a second ASRG on the carrier that would keep operating after the in-situ element is delivered. Based on the results of this and another eight ongoing NASA funded studies, NASA will make a decision about the inclusion of ASRGs in the next Discovery AO, due in the summer of 2009.
TI: The Titan Saturn System Mission
AB: A mission to return to Titan after Cassini-Huygens is a high priority for exploration. Recent Cassini-Huygens discoveries have revolutionized our understanding of the Titan system, rich in organics, containing a vast subsurface ocean of liquid water, surface repositories of organic compounds, and having the energy sources necessary to drive chemical evolution. With these recent discoveries, interest in Titan as the next scientific target in the outer Solar System is strongly reinforced. Cassini's discovery of active geysers on Enceladus adds an important second target in the Saturn system.
The mission concept consists of a NASA-provided orbiter and an ESA-provided probe/lander and a Montgolfiere. The mission would launch on an Atlas 551 around 2020, travelling to Saturn on an SEP gravity assist trajectory, and reaching Saturn about 9.5 years later. The flight system would go into orbit around Saturn for about 2 years. During the first Titan flyby, the orbiter would release the lander to target a large northern polar sea, Kraken Mare, and the balloon system to a mid latitude region.
During the tour phase, TSSM will perform Saturn system and Enceladus science, with at least 5 Enceladus flybys. Instruments aboard the orbiter will map Titan's surface at 50 m resolution in the 5 micron window, provide a global data set of topography and sound the immediate subsurface, sample complex organics, provide detailed observations of the atmosphere, and quantify the interaction of Titan with the Saturn magnetosphere. A subset of the instruments would provide spectra, imaging, plume sampling and particles and fields data on Enceladus.
Instruments aboard the balloon will acquire high resolution vistas of the surface of Titan as the balloon cruises at 10 km altitude, as well as make compositional measurements of the surface, detailed sounding of crustal layering, and chemical measurements of aerosols. A magnetometer, will permit sensitive detection of induced or intrinsic fields.
The probe/lander will splash into a large northern sea and spend several hours floating during which direct chemical and physical sampling of the liquid would be undertaken. During its descent the probe would provide the first in situ profiling of the winter northern hemispheric atmosphere, distinctly different from the equatorial atmosphere where Huygens descended and the balloon will arrive. Radio science experiments should be capable of providing detailed information on Titan's tidal response, and hence its crustal rigidity and thickness.
TI: Cassini Radar: Extended Mission Plans and Expected Results
AB: Cassini completed its four year Prime Mission in July, 2008. This included a total of 45 close Titan flybys, with radar data obtained on 23 of these. An approved two year extended mission will provide an additional 25 close Titan flybys, with radar data collected on 12 of these. The prime mission radar data covered primarily the northern hemisphere of Titan, and the priority for the extended mission radar observations will be to fill in southern hemisphere coverage and provide limited repeat coverage for change detection in the north. During the prime mission, all but one flyby included some form of synthetic aperture imaging, leading to a wide range of viewing geometries. Imaging resolution varied from 300-500 m at the closest approach altitudes (1000 km) to about 2 km during high altitude (20,000 km) imaging segments. Altimetry, scatterometry, and radiometry mode data were also collected over multiple geometries to sample Titan's scattering and emission functions. The varying geometry and instrument parameters, which lead to varying resolution, SNR, polarization, incidence angle and noise characteristics, must be properly accounted for when interpreting these data. Here we review the coverage and other important characteristics of the radar data sets obtained at Titan in the prime mission, and compare these with plans for the extended mission. The first extended mission radar observation will occur on Dec 5, 2008, and we will present these timely preliminary results if the spacecraft operates as planned. Prime mission data along with corresponding surface coverage from ISS and VIMS have revealed a diverse Titan surface, which will be further augmented and analyzed by extended mission results. This work is supported by the NASA Cassini Program at JPL - Caltech.
TI: A Venus Flagship Mission: Exploring a World of Contrasts
AB: Results from past missions and the current Venus Express Mission show that Venus is a world of contrasts, providing clear science drivers for renewed exploration of this planet. In early 2008, NASA's Science Mission Directorate formed a Science and Technology Definition Team (STDT) to formulate science goals and objectives, mission architecture and a technology roadmap for a flagship class mission to Venus. This 3- to 4 billon mission, to launch in the post 2020 timeframe, should revolutionize our understanding of how climate works on terrestrial planets, including the close relationship between volcanism, tectonism, the interior, and the atmosphere. It would also more clearly elucidate the geologic history of Venus, including the existence and persistence of an ancient ocean. Achieving these objectives will provide a basis to understand the habitability of extra solar terrestrial planets. To address a broad range of science questions this mission will be composed of flight elements that include an orbiter that is highlighted by an interferometric SAR to provide surface topographic and image information at scales one to two orders of magnitude greater than that achieved by any previous spacecraft to Venus. Two balloons with a projected lifetime of weeks will probe the structure and dynamics of the atmosphere at an altitude of 50 to 70-km. In addition, two descent probes will collect data synergistic to that from the balloon and analyze the geochemistry of surface rocks over a period of hours.