Europa Planetary Protection for Juno Jupiter Orbiter
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Accepted Manuscript Europa Planetary Protection for Juno Jupiter Orbiter Douglas E. Bernard, Robert D. Abelson, Jennie R. Johannesen, Try Lam, William J. McAlpine, Laura E. Newlin PII: S0273-1177(13)00151-8 DOI: http://dx.doi.org/10.1016/j.asr.2013.03.015 Reference: JASR 11293 To appear in: Advances in Space Research Received Date: 9 August 2012 Revised Date: 21 February 2013 Accepted Date: 3 March 2013 Please cite this article as: Bernard, D.E., Abelson, R.D., Johannesen, J.R., Lam, T., McAlpine, W.J., Newlin, L.E., Europa Planetary Protection for Juno Jupiter Orbiter, Advances in Space Research (2013), doi: http://dx.doi.org/ 10.1016/j.asr.2013.03.015 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 1 2 3 4 5 Europa Planetary Protection for Juno Jupiter Orbiter 6 7 Douglas E. Bernard, Robert D. Abelson, Jennie R. Johannesen, Try Lam, William J. 8 McAlpine, and Laura E. Newlin 9 10 11 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, 12 Pasadena, CA 91109, USA, [email protected], 13 [email protected], [email protected], 14 [email protected], [email protected], [email protected] 15 16 17 © 2011 California Institute of Technology. Government sponsorship acknowledged. 18 19 Abstract 20 21 22 NASA's Juno mission launched in 2011 and will explore Jupiter and its near 23 environment starting in 2016. Planetary protection requirements for avoiding the 24 contamination of Europa have been taken into account in the Juno mission 25 26 design. In particular Juno's polar orbit, which enables scientific investigations of 27 parts of Jupiter's environment never before visited, also greatly assist avoiding 28 close flybys of Europa and the other Galilean satellites. 29 30 The science mission is designed to conclude with a deorbit burn that disposes 31 32 of the spacecraft in Jupiter’s atmosphere. Compliance with planetary protection 33 requirements is verified through a set of analyses including analysis of initial 34 bioburden, analysis of the effect of bioburden reduction due to the space and 35 Jovian radiation environments, probabilistic risk assessment of successful 36 37 deorbit, Monte-Carlo orbit propagation, and bioburden reduction in the event of 38 impact with an icy body. 39 40 41 1. Introduction 42 43 44 NASA’s next mission to the outer planets will send a spacecraft to Jupiter for 45 a detailed scientific investigation of the planet itself. The Juno mission—named 46 for the mythological wife of the Roman god Jupiter—was launched in 2011 and 47 will arrive at Jupiter in 2016. Like the eponymous Roman Juno, the Juno mission 48 49 is designed to figuratively brush away the clouds to learn about Jupiter’s true 50 behavior. NASA’s New Frontiers Program selects among competing high- 51 science-return Principal Investigator-led planetary science investigations. In 52 2005, NASA selected Juno as the second mission of this Program with Scott 53 54 Bolton of Southwest Research Institute as the Principal Investigator. Juno is 55 managed by the California Institute of Technology’s Jet Propulsion Laboratory 56 (JPL). 57 58 Juno’s highly elliptical polar orbit and low perijove (above the cloud tops by 59 about 7% of Jupiter’s radius) allow it to explore portions of the Jovian 60 61 62 63 64 65 1 2 3 4 environment never before visited. Its suite of instruments is designed to 5 6 investigate the atmosphere, gravitational fields, magnetic fields, and auroral 7 regions of Jupiter from this vantage point. This orbit also helps avoid or limit 8 exposure to the most intense portion of Jupiter’s radiation belts. This limited 9 radiation exposure, along with the low-power spacecraft and instrument design, 10 make it possible for Juno to perform its observation using solar power – making it 11 12 the first solar-powered mission to the outer planets. 13 14 The Juno mission is not orbiting or flying close to Europa or any other 15 Galilean satellite – its polar orbit does not even bring it close to them. 16 Nevertheless, planetary protection requirements for avoiding the contamination 17 18 of Europa have been taken into account in the Juno mission design. 19 20 The science mission is designed to conclude with a deorbit burn that disposes 21 of the spacecraft in Jupiter’s atmosphere. Compliance with planetary protection 22 (PP) requirements is verified through a set of analyses including analysis of initial 23 bioburden, analysis of the effect of bioburden reduction due to the space and 24 25 Jovian radiation environments, probabilistic risk assessment of successful 26 deorbit, Monte Carlo orbit propagation, and bioburden reduction due to impact 27 with an icy body. 28 29 This paper discusses the Juno mission’s approach to meeting planetary 30 31 protection requirements for missions in orbit at Jupiter. The approach that meets 32 Europa planetary protection requirements easily meets planetary protection 33 requirements for the other Galilean satellites, so this paper focuses on Europa. 34 35 2. Juno Overview 36 37 38 Juno is a science mission, so this overview starts with the science objectives. 39 The mission design and spacecraft design are then outlined. 40 41 2.1. Science 42 43 44 The overall goal of the Juno mission is to improve our understanding of the 45 solar system by understanding the origin and evolution of Jupiter. The science 46 objectives for Juno are laid out in the New Frontiers Program Plan: 47 48 49 Atmospheric Composition: Juno investigates the formation and origin 50 of Jupiter’s atmosphere and the potential migration of planets through 51 the measurement of Jupiter’s global abundance of oxygen (water) and 52 nitrogen (ammonia). 53 54 Atmospheric Structure: Juno investigates variations in Jupiter’s deep 55 atmosphere related to meteorology, composition, temperature profiles, 56 cloud opacity, and atmospheric dynamics. 57 58 Magnetic Field: Juno investigates the fine structure of Jupiter’s 59 magnetic field, providing information on its internal structure and the 60 nature of the dynamo. 61 62 63 2 64 65 1 2 3 4 Gravity Field: Gravity sounding by Juno explores the distribution of 5 6 mass inside the planet. 7 Polar Magnetosphere: Juno explores Jupiter’s three-dimensional polar 8 magnetosphere and aurorae. 9 10 11 The science objectives will be accomplished by a payload suite supporting 9 12 investigations: a magnetometer (MAG), a microwave radiometer (MWR), a 13 gravity science experiment using the spacecraft’s X-band communications 14 15 system plus a Ka-band translator, a plasma instrument with four sensors to 16 measure electron and ion particle distributions (JADE), an energetic particle 17 detector with three sensors (JEDI), a electromagnetic field sensor (Waves), an 18 ultraviolet imaging spectrometer (UVS), an infrared imaging spectrometer 19 (JIRAM), and an optical camera (JunoCam) (Matousek, 2005). 20 21 22 2.2. Interplanetary Trajectory 23 24 Juno was launched from Cape Canaveral Air Force Station in August 2011 on 25 an Atlas V 551 launch vehicle. The Juno spacecraft interplanetary trajectory to 26 27 Jupiter is shown in Figure 1. After separation of the spacecraft from the launch 28 vehicle, the flight system (spacecraft) began an almost 5-year cruise phase to 29 Jupiter with two Deep Space Maneuvers (DSM) roughly at aphelion (~ 1 year 30 after launch), and an Earth flyby (EFB) at 500 km altitude, 26 months after 31 32 launch. The spacecraft will arrive at Jupiter in July 2016. Interplanetary cruise 33 concludes with a Jupiter Orbit Insertion (JOI) burn that places Juno into a polar 34 107-day capture orbit around Jupiter. 35 36 Only the spacecraft and the upper stage escape Earth orbit. Earth and Jupiter 37 are the only solar system bodies encountered—at no time does the spacecraft 38 39 come closer than 1.6 AU to Mars. 40 41 2.3. Orbital Mission 42 43 At Jupiter, Juno’s initial 107-day capture orbit and its ~11-day science orbits 44 45 are all polar orbits, allowing unprecedented views of the North and South polar 46 regions and in-situ measurements at all latitudes. See Figure 2. The red circles in 47 Figure 2 represent the orbits of Io, Europa, Ganymede, and Callisto (in 48 increasing distance from Jupiter). The Period Reduction Maneuver (PRM) at the 49 50 end of the capture orbit sets up the 10.9725-day orbit that keeps each 51 successive perijove (PJ) visible at the Goldstone Deep Space Network (DSN) 52 complex in California. This timing is necessary so that mapping of the gravity 53 field at Jupiter may be done using X-band and the Ka-band uplink/downlink 54 capability at that complex. The precise timing of the orbit period is achieved by 55 56 an Orbit Trim Maneuver (OTM) scheduled 4 hours after each perijove; this 57 enables the equator crossings to be equally spaced with respect to each other. 58 Following the full set of science orbits plus one spare orbit, the spacecraft will 59 perform a deorbit maneuver near apojove of the last orbit to impact Jupiter, 60 61 62 63 3 64 65 1 2 3 4 thereby ending the mission and providing continued avoidance of the Galilean 5 6 satellites as required for planetary protection.