VERITAS, EnVision and a Venus Program

Suzanne Smrekar1, Scott Hensley1, Darby Dyar2, Jörn Helbert3, and the VERITAS Science Team, (1) Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA USA (ssmrekar@jpl.nasa.gov, [email protected]), (2) Dept. of Astronomy, Mount Holyoke College, South Hadley, MA USA ([email protected]), (3) Inst for Planetary Research, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany ([email protected]).

Introduction: At this meeting, many will make the case for the repeat pass radar interferometry. It is also an essential input to many compelling science questions that can be achieved via the data reduction for VEM in tessera because temperature as orbital radar and near-IR spectroscopy, and gravity science. This function of elevation much be removed. abstract discusses and contrasts the mature VERITAS mission concept and the anticipated EnVision mission capabilities, their Every time Mars has been observed at roughly an order of complementarity, and their role in enabling and motivating a magnitude higher resolution, entirely new and often unexpected suite of future missions that could form a scientifically rich processes have been observed. The global context of these program [1]. Just as there have been numerous imaging systems discoveries provides immensely important insights on a planet’s at Mars, there is great value in different Venusian radar missions. evolution and point to scientific treasure troves that have made landed missions so successful on Mars [8]. Topography further VERITAS is a proposed NASA Discovery mission. provides the quantitative information needed to discriminate Selections for missions advancing to step 2 will likely be between hypotheses for formation [9]. The HiRISE camera (25 announced prior to the EnVision conference. VERITAS is a cm pixels) at Mars is an excellent example of how low areal mature concept that has been proposed previously and very coverage at high resolution can be highly scientifically valuable. favourably reviewed by past, rigorous NASA review boards. If However, the value of its targeting has been greatly enhanced by VERITAS moves forward, selections for VERITAS and global Context camera data (6m pixel). VERITAS’ global EnVision will be made roughly simultaneously. VERITAS imaging (30 m) and EnVision’s highest resolution imaging (10 would launch to and arrive at Venus in 2026. After aerobraking, m) are analogous. Moreover, the minimum 10-year span of it would begin taking science data in its final orbit in 2028 and combined surface observations by the two missions at Venus conduct science for 4 Venus cycles. If the mission is healthy, it would enhance our understanding of Venus geology the way over is likely that NASA would extend the mission for future cycles. two decades of Mars observations from orbit have improved Martian geology and geophysics. VERITAS would carry two instruments: VISAR and VEM. The Venus Interferometric Synthetic Aperture Radar (VISAR) X- Orbital missions lay the ground work for future surface missions, band [2] measurements include: 1) a global digital elevation just as been done for Mars and the moon, and is under model (DEM) with 250 m postings, 5 m height accuracy, 2) consideration for other bodies. Further, VERITAS and EnVision Synthetic aperture radar (SAR) imaging at 30 m horizontal would pave the way for a Venus Program [1], that could include resolution globally, 3) SAR imaging at 15 m resolution for landed or aerial platform missions to investigate the highest value targeted areas, and 4) surface deformation from RPI at 2 mm science targets discovered from orbit. Venus is an incredibly rich precision for 12 200x200 km targeted, potentially active areas. scientific target worthy of a program of scientific missions. Community input would be solicited for both RPI and high- resolution imaging targets. VEM [3] would produce surface Acknowledgements: A portion of this research was conducted coverage of most of the surface in 6 NIR bands located within 5 at the Jet Propulsion Laboratory, California Institute of atmospheric windows and of 8 atmospheric bands for calibration Technology, under contract with NASA. The information and water vapor measurements. VERITAS also conducts radio presented about the VERITAS mission concept is pre-decisional science. Magellan spherical harmonic gravity field has an and is provided for planning and discussion purposes only. average resolution of only 550 km [4]. Rigorous modelling shows that VERITAS data, with an average resolution of 165 km, References: [1] Helbert, J., D. Dyar, and N. Izenberg, this would enable estimation of elastic thickness-a proxy for thermal meeting. [2] S. Hensley, J. Martin, S. Oveisgsharan, X. Duan, gradient [5] and resolution of specific geologic processes [6]. and B. A. Campbell, "Radar Performance Modeling for Venus," VEXAG Meeting, Applied Physics Laboratory, 2018. Complementary Missions: To the casual observer, VERITAS [2] J. Helbert, D. Dyar, I. Walter, D. Wendler, T. Widemann, E. and EnVision appear similar, as both carry a radar, VEM, and do Marcq, et al., "The Venus Emissivity Mapper (VEM): obtaining gravity science. However, VERITAS and EnVision have distinct global mineralogy of Venus from orbit," in infrared Remote instrument capabilities and measurement objectives. EnVision’s Sensing and Instrumentation XXVI 2018, p. 99730R. [4] radar is at S-band, and focuses on targeted, high resolution Konopliv A., Banerdt, W.B., and W.L. Sjogren, Venus Gravity: imaging [7]. Targeted high resolution topography is conducted 180th Degree and Order Model, Icarus 139, 3-18, 1999. via stereo topography from imaging, rather than from [5] M. A. Wieczorek, Gravity and Topography of the Terrestrial interferometry [8]. Low resolution topography is obtained from Planets, Treatise on Geophysics, vol. 10, pp. 165-206, 2007. it radar sounder and S-band radar altimetry. EnVision also has a [6] Andrews-Hanna J. C., S. Smrekar, E. Mazarico, Venus radiometer mode. Additionally, the timelines for the two Gravity Gradiometry: Plateaus, Chasmata, Coronae, and the missions are highly complementary. VERITAS and EnVision. Need for a Better Global Dataset LPSCXLVII Abst. #2907, 2016. [7] would start acquiring data in 2027 and 2035, respectively. Ghail, R. et al., Int. J. App. Earth Obs. Geoinfo., 2017. [8] Hensley et al., this meeting. [9] Hand, E., The Mars Observer, Nature, VERITAS’ global datasets would provide valuable context for v479, 2011. [10] Zimbelman, J. R. Image resolution and higher resolution EnVision imaging and stereo topography. evaluation of genetic hypotheses for planetary landscapes, Global high-resolution topography is also of value for removing Geomorph. 37, 179, 2001. clutter for radar sounding and supporting more widely dispersed