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E Panel Missions Not Selected for Additional Study INTRODUCTION As described in Appendix C, each of the surveyâs six panels reviewed the SDT and PMCS reports and assessed those concepts proposed by the community in white papers and prior proposals. Then the panels identified 18 additional large- and medium-class mission concepts that could address key scientific questions within their respective purviews. Following documentation by their originating groups, the steering group assessed each of these concepts and selected nine for additional study. This appendix describes the nine concepts that were not selected for additional study. These concepts are as follows, in no specific order: â¢ VISANâVenus in situ seismic and atmospheric network; â¢ VSCAâVenus sub-cloud aerobot; â¢ VLPâVenus life potential; â¢ VIDEOâVenus investigation of dynamics from an equatorial orbit, â¢ Mars Deep Time Rover; â¢ Mars Polar Ice, Climate and Organics; â¢ Saturn Ring Skimmer; â¢ Interstellar Object Rapid Response Mission; and â¢ Solar System Space Telescope. The following sections describes these nine concepts VENUS IN SITU SEISMIC AND ATMOSPHERIC NETWORK Origin and Goals This concept was proposed by the Panel on Venus to address the following goals: â¢ Determine if Venus is seismically and/or volcanically active; â¢ Characterize the interior structure and thermal state of Venus; â¢ Establish meteorological conditions at the Venus surface; and â¢ Determine the morphology of the Venus surface at various spatial scales. Implementation This concept was proposed as a potential medium-class mission and implemented by five long-long landers and a supporting orbiter. The landers touch down in a pre-planned array within 500 Â±200 km of one another. The orbiter acts as communications relay and searches for seismic activity via airglow emissions. PREPUBLICATION COPY â SUBJECT TO FURTHER EDITORIAL CORRECTION E-1
Nature of Study Requested The panel requested that a rapid mission architecture (RMA) study (i.e., Concept Maturity Level CML ~1-3) be undertaken to assess the feasibility of precisely landing multiple assets simultaneously or in series, and sustaining communication. VENUS SUB-CLOUD AEROBOT Origin and Goals This concept was proposed by the Panel on Venus to address the following goals: â¢ Establish the early evolution of Venus and determine if liquid water was ever present; â¢ Measure atmospheric dynamics and composition on Venus; and â¢ Characterize the geologic history preserved on the surface of Venus. Implementation This concept was proposed as a potential medium- or large-class mission and implemented by a variable-altitude aerial platform and a supporting orbiter. The aerobot would conduct near-infrared imaging and spectroscopy from an altitude of at 47 km (cf. 56-61 km for the aerobot component of the Venus Flagship concept). The concept envisaged that either entire platform descends to the requisite altitude or that a tethered instrument platform is lowered from an aerobot at a higher altitude. Nature of Study Request The panel requested a low-fidelity (CML ~1-3) study to descope the PMCS Venus Flagship mission and redesign it to focus on the feasibility of using an aerobot to conduct sub-cloud investigations. VENUS LIFE POTENTIAL Origin and Goals This concept was proposed by the Panel on Venus to address the following goals: â¢ Characterize Venusâ water history based on geologic and atmospheric markers; â¢ Characterize Venusâ ultraviolet absorption component and its interdependency on atmospheric conditions; and â¢ Identify Venusâ atmosphere and surface chemistry and the potential for extant cloud life. PREPUBLICATION COPY â SUBJECT TO FURTHER EDITORIAL CORRECTION E-2
Implementation This concept was proposed as a large-class mission and implemented via an orbiter, a large lander, and a fixed-altitude aerial platform. The orbiter is in a high, equatorial, retrograde orbit (cf. versus the vs. polar orbit for radar-equipped VFM. The lander is designed to target a representative radar-smooth plains unit at low latitudes (cf. versus the tesserae for the Venus Flagship mission) Nature of Study Requested The panel requested a full study (i.e., CML ~4-5) using the Venus Flagship as its starting point to investigate an alternate to concept emphasizing a focus on the current potential for life in the Venus clouds. VENUS INVESTIGATION OF DYNAMICS FROM AN EQUATORIAL ORBIT Origin and Goals This concept was proposed by the Panel on Venus to address the following goals: â¢ Characterize the dynamics within the Venus atmosphere; â¢ Measure the chemistry of the Venus atmosphere; â¢ Characterize the Venus ionosphere and types and rates of atmospheric escape; â¢ Determine if Venus is seismically and/or volcanically active; and â¢ Establish the composition of major geological units on Venus. Implementation This concept was proposed as a large-class mission and implemented via an orbiter, SmallSats, a fixed- altitude aerial platform, a small lander, and dropsondes. The orbiter is placed in a high, equatorial orbit (cf. versus the polar orbit of the Venus Flagship) so that it can continuously monitors the entire planetary disk, and thus increased communication duration with lander and aerial platform. Nature of Study Requested The panel requested a full study (i.e., CML ~4-5) using the Venus Flagship as its starting point to create a new concept emphasizing the study of atmospheric dynamics and the planetâs super-rotation. MARS DEEP TIME ROVER Origin and Goals This concept was proposed by the Panel on Mars to investigate Marsâs Noachian/Pre-Noachian terrains: the solar systemâs only preserved geologic record of the emergence of a habitable world (>3.5 billion years ago). The widespread presence of clay minerals in these terrains indicate long-duration water-rock interaction in environments whose nature is indeterminate from orbit. Examination of such terrains addresses the following goals relating to fundamental processes occurring during the first billion years in the evolution of habitable worlds, in that it would: PREPUBLICATION COPY â SUBJECT TO FURTHER EDITORIAL CORRECTION E-3
â¢ Determine the composition and history of Pre-Noachian and Noachian martian units, volcanic, sedimentary, and groundwater/hydrothermal; â¢ Determine the suites of habitable conditions present on early Mars and what controls observed variability over space and time; â¢ Evaluate the surface inventory of water and other volatiles, including change with time by isotopic and mineralogical/chemical analysis; and â¢ Measure, if feasible, the ages of rock units and surfaces. Implementation This concept was proposed as medium-class mission and implemented via a rover using an upgraded air bag landing system and having greater operating autonomy than its MER predecessors. The rover would carry mast and navigational cameras, an infrared spectrometer, magnetometer, mass spectrometer, and meteorological package, as well as an arm-mounted X-ray and MÃ¶ssbauer spectrometers, and, a microscope. The arm would carry a rock-powder acquisition system. Nature of Study Request The panel requested a full mission study (i.e., CML ~4-5) to assess if the PMCS Intrepid lunar rover concept could be adapted for use on Mars. Among the issues to be assessed during the study were the following: can the landing ellipse be reduced to <25 km; can the rover drive 300 m per day; is the feasible to incorporate a sample-handling system and a mass spectrometer on an MER-class rover; and is a solar power system sufficient? MARS POLAR ICE, CLIMATE AND ORGANICS Origin and Goals This concept was proposed by the Panel on Mars to understand the processes controlling the modern- day evolution of the martian climate by studying the climatic record encoded in the northern polar layered deposits (NPLD). Such studies are needed to connect orbital measurements of NPLD with modeling of climate change induced by variations in the planetâs orbital elements over the last 10 million years. The specific goals of the proposed mission are as follows: â¢ Measure the composition, structure, and sub-mm layering of ice and dust contained in the top 2 m of the NPLD; â¢ Quantify the evolution of the NPLD surface, including the net accumulation of dust and ice over one martian year; â¢ Measure the present-day surface energy balance and the fluxes of heat, momentum, dust, and volatiles between the atmosphere and surface over one martian year; and â¢ Measure the polar atmospheric circulation and the transport of water and dust in the planetary boundary layer over one martian year. Implementation This concept was proposed as a medium-class lander equipped with a drill capable of penetrating at PREPUBLICATION COPY â SUBJECT TO FURTHER EDITORIAL CORRECTION E-4
least 50 cm (ideally 2 m) into ice layers for both in situ measurement. Extraction of samples and their delivery instruments mounted on the spacecraftâs deck is also required. The spacecraft lands on ice-covered NPLD shortly after the loss of the north polar seasonal ice cap. Drilling continues through the summer and is followed by meteorological and flux measurements for the remainder of one martian year. Instruments include: a meteorology and flux package; borehole microscopic imager and a thermoelectric conductivity probe, as well as a suite of sample analysis instruments on the landerâs deck for compositional measurements. Nature of Study Request The panel requested a full study (CML ~4-5) to investigate the adaptation of the ICE-SAG (MEPAG 20XX) and Vision and Voyages polar lander (NASEM 2011, p. 362) concepts to one full Mars year of operations and the use of a radioisotope power source. The study would also assess how to optimize the drill and on-board instrumentation for the search for organic material in the ice. SATURN RING SKIMMER Origin and Goals This concept was proposed by the Panel on Giant Planet Systems to address the following goals: â¢ Quantify the processes operating in particle-rich astrophysical disks, including particle aggregation and fragmentation; and â¢ Probe the origins and history of Saturnâs rings. Implementation This concept was proposed as a medium-class Saturn orbiter in a low-inclination orbit (pericenter 90,000-to-130,000 km to avoid both the F and main rings). Repeated passes over the rings at altitudes <1,000 km (cf. 100 times lower than Cassini) will enable extremely high-resolution imaging and sampling the material flowing between the rings and the planet. To maintain pointing at one location (not predetermined) in the rings for at least 1,000 seconds requires that the spacecraft incorporate a scan platform or be able to slew. The in situ instruments are pointed in the appropriate ram directions to obtain sufficient fluxes to measure composition or be slewed to constrain particle and molecular velocity distributions. Instruments include: a high-resolution camera (to image five regions in the rings at â¤1 m spatial resolutions, taking at least four images of the same region separate in time by at least ~250 seconds); a dust detector (capable of sensing particles down to 10 nm in radius, determining particle masses and velocities, and sensitive enough to measure dust fluxes from the rings between 10-15-and-10-13 kg/m2/s and densities between 1-and-1000 /cm3 over each of the main rings); and an ion and neutral mass spectrometer (capable of sensing between l-and-l 00 amu, determining molecule velocities and sensitive enough to measure average ion/molecule fluxes between from the rings between 10-15 and l0-13 kg/m2/s and densities between 0.1-and-105 /cm3 over each of the main rings). The instruments are also required to measure the mass fractions of the material flowing out of the rings in the form of water, organics and silicates to an accuracy of at least 10 percent and determine isotope ratios for selected CHO materials. Nature of Study Request The panel requested a full mission study (i.e., CML ~4-5). PREPUBLICATION COPY â SUBJECT TO FURTHER EDITORIAL CORRECTION E-5
INTERSTELLAR OBJECT RAPID RESPONSE MISSION Origin and Goals This concept was proposed by the Panel on Small Solar System Bodies to investigate the acquisition of time-critical spacecraft observations of novel solar system phenomena. The discovery of the first interstellar objectsâ1I/âOumuamua in 2017 and 2I/Borisov in 2019âtransiting the solar system was one of the key scientific result of the last decade. When NSFâs Vera C. Rubin Observatory becomes operational later this decade, the rate at which interstellar objects are discovered is expected to rise to one per year. The ability to design, develop, and deploy a spacecraft mission on a prompt timescale is also of interest for addressing other classes of opportunistic objects (e.g., Oort cloud comets) and for planetary defense purposes (see Chapters 18 and 22). However, the current structure of mission opportunities within NASAâs Planetary Science Division does not lend itself to opportunistic, rapid response missions to newly identified targets of high scientific value. Therefore, the goal of the study is to investigate novel programmatic approached to the rapid procurement, development, and targeting of objects of intrinsic scientific or societal interest. Implementation This concept was proposed as an examination of novel mission architectures to enable small-class spacecraft to undertake rapid response missions in the next decade. Three principal architectures are to be considered. First, build the spacecraft and store on ground until needed. Second, build the spacecraft and store in space until discovery of the object of interest (e.g., ESA Comet Interceptor). Third, build the spacecraft after the discovery of the object of interest. Nature of Study Request The panel requested that an RMA study (i.e., CML ~1-3|) be undertaken to assess the feasibility, resource, and cost implications of the three programmatic architectures described above. Also, to be examined were the benefits and consequences of a redundant multi-spacecraft architecture. SOLAR SYSTEM SPACE TELESCOPE Origin and Goals This concept was proposed by a cross-panel group to promote new innovative science and to support and exploit discoveries made by past/current/future missions to specific targets. A space telescope dedicated to observations of solar system bodies would benefit the planetary science community by enabling capabilities beyond those of current astrophysics missions and provide more opportunities for high-priority solar system science studies. The goals of the telescope are as follows: â¢ Provide significant improvement in capability and mission timeline compared to current observatories to explore dynamic processes and systems via long baseline time-domain measurements; and â¢ Expand spectroscopic mapping and improves angular resolution of small body populations, including KBOs PREPUBLICATION COPY â SUBJECT TO FURTHER EDITORIAL CORRECTION E-6
Implementation This concept was proposed as a medium-class, 2-to-10-m dedicated telescope with ultraviolet/visible/near-infrared imaging and spectroscopic capabilities, optimized for cadence and survey observations of transient, evolving, and interacting processes in the solar system. Desirable characteristics include the following: ability to operate at solar elongations â¥30Â°; a tracking capability of â¥216â/hr; instrument field of view of 60â; and minimum lifetime of 7 years. Nature of Study Request The cross-panel group requested that an RMA study (i.e., CML ~1-3) be undertaken to investigate the benefits of a dedicated solar system space telescope, to perform trade studies to define an overall optimal architecture and payload, and to demonstrate feasibility within the constraints of the New Frontiers program. PREPUBLICATION COPY â SUBJECT TO FURTHER EDITORIAL CORRECTION E-7