Planetary Science Vision 2050 Workshop 2017 (LPI Contrib. No. 1989) 8097.pdf

JUpiter MagnetosPheric boundary ExploreR (JUMPER). R. W. Ebert1 F. Allegrini1,2, F. Bagenal3, C. Beebe1, M. I. Desai1,2, D. George1, J. Hanley1, N. Murphy4, and A Wolf4, 1Southwest Research Institute, 6220 Culebra Rd., San Antonio, TX USA 78238 ([email protected]) 2University of Texas at San Antonio, One UTSA Circle, San Anto- nio, TX USA 78249 3Laboratory for Atmospheric and Space Phyiscs, University of Colorado, 1234 Innovation Dr, Boulder Colorado, USA 80303 4Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena California, USA 91109.

Mission Summary: We present the JUpiter Mag- Mission Science: JUMPER addresses open ques- netosPheric boundary ExploreR, JUMPER, a Jupiter tions related to (i) how the solar wind couples to the orbiting SmallSat mission concept to explore the plan- jovian magnetosphere and (ii) influences magneto- et’s magnetospheric boundaries and image its energetic spheric dynamics, and (iii) how energetic neutral at- neutral atom (ENA) emissions. JUMPER’s science oms contribute to mass loss from Jupiter’s magneto- objectives focus on how the solar wind interacts with sphere. These questions are addressed through the fol- Jupiter’s magnetosphere and the contribution of ENAs lowing science objectives:. to mass loss from the jovian space environment. These Objective 1) Characterize the solar wind upstream objectives will be met with a science payload consist- of Jupiter’s magnetosphere and provide context for ing of two ion sensors, a magnetometer, and an ENA studying magnetospheric dynamics by a primary imager. Measurements from these instruments will spacecraft. One of the more hotly debated questions complement simultaneous observations of Jupiter’s related to Jupiter is to what extent does the solar wind magnetosphere from a primary spacecraft (e.g. Europa influence its magnetosphere? While the dynamics of Multiple Flyby Mission, Jupiter Icy moons Explorer, the magnetosphere are largely driven by the planet’s Io Observer, etc.), providing a multi-point platform 10-hour rotation period, the contribution from the solar from which to study the dynamics of this system. The wind is not well understood. Magnetospheric processes science objectives, which have yet to be addressed by with evidence of solar wind influence include the mo- any other Jupiter mission, are responsive to the NASA tion of Jupiter’s bow shock and magnetopause [1], the Planetary Science Division (PSD) science goal – Ad- opening and closing of magnetic flux in the outer mag- vance the understanding of how the chemical and netosphere [2, 3], the transport of mass, energy, and physical processes in our solar system operate, interact, momentum into the magnetosphere [4], variations in and evolve –as defined in NASA’s 2014 Science Plan. ultraviolet (UV) auroral emissions and morphology JUMPER’s science objectives drive several top- [5], auroral radio emission enhancements [6,7] and level requirements on mission design. The most im- current sheet asymmetries in the magnetotail [8]. portant is an orbit that includes several passes through While the solar wind and interplanetary magnetic field Jupiter’s bow shock and magnetopause on the dayside (IMF) at Jupiter’s orbital distance have been studied in of Jupiter. Mission design is also constrained by the detail [9, 10], our lack of understanding stems from, in necessity to ride share on a primary vehicle, at least part, the absence of a solar wind monitor upstream of until after Jupiter orbit insertion. Jupiter when the magnetosphere was being observed. The JUMPER spacecraft design derives heritage JUMPER will address this topic by placing a from SmallSats developed for the Southwest Research SmallSat into orbit around Jupiter with an apojove Institue (SwRI)-led Cyclone Global Navigation Satel- beyond the nominal position of Jupiter’s bow shock. lite System (CYGNSS) mission. It consists of an JUMPER will measure the solar wind ions and IMF Evolved Expendable Launch Vehicle Secondary Pay- upstream of Jupiter’s magnetosphere to complement load Adapter (ESPA) compatible frame supporting simultaneous observations of the magnetosphere four double-deployed solar array panels, ESPA ring and/or aurora from a primary spacecraft. These simul- interconnections, four science instruments, and a radia- taneous observations will be key to obtaining a more tion vault to house the spacecraft avionics and payload complete understanding of the physics governing this subsystem electronics. JUMPER will use its perijove system. periods to transmit data to the primary spacecraft and Objective 2) Investigate the modes of solar wind cou- execute ranging activities. It will de-orbit into Jupiter pling (e.g. magnetic reconnection, Kelvin-Helmholtz waves) at end of mission. along Jupiter’s dayside magnetopause. Another important While the JUMPER mission focuses on Jupiter, open topic is how the solar wind interacts with Jupi- this concept can be applied, with modifications, to any ter’s magnetopause. This has important implications planetary system, preferably one where there’s an in- for outer magnetosphere dynamics, especially the teraction between the solar wind and the planet’s in- transport of mass, energy, and momentum into the trinsic or induced magnetic field. magnetosphere and the circulation of open magnetic flux. The two primary modes of interaction are thought Planetary Science Vision 2050 Workshop 2017 (LPI Contrib. No. 1989) 8097.pdf

to be magnetic reconnection [11] and shear-flow driv- Mission Design en instabilities [4]. Evidence of magnetic reconnection The most important mission design requirement for has been limited to a few magnetopause crossings with JUMPER is an orbit that includes several passes signatures observed primarily in the magnetic field through Jupiter’s bow shock and magnetopause on the observations [12, 13] and more recently in the form of dayside of Jupiter. Our baseline concept is a 1 year accelerated ions flows [14]. Evidence of wave activity mission with six orbits, each having an apojove a dis- at Jupiter’s magnetopause, such has the Kelvin- tance of ~140 RJ. Helmholtz instability, is essentially non-existent. Our The baseline spacecraft design consists of an ESPA lack of knowledge on the processes operating at Jupi- compatible frame supporting four double-deployed ter’s magnetopause is primarily due to the limited solar array panels, ESPA ring interconnections, and number of spacecraft observations taken over a limited four science instruments positioned to accommodate spatial extent [15]. their field-of-views (FOVs). Embedded within the JUMPER will help address this key question by frame is an electronics vault that will house a majority measuring the ion velocity distributions and flows and of the electronics for the spacecraft avionics and pay- the magnetic field in the vicinity Jupiter’s dayside load subsystems. The nominal flight system consists of magnetopause to look for signatures of these process- 5 subsystems: 1) Command and Data Handling es. JUMPER’s orbit places the spacecraft in a favora- (C&DH), 2) Electrical Power System (EPS), 3) Com- ble location to cross the magnetopause multiple times munication and Data System (CDS), 4) Attitude De- as it drifts along Jupiter’s dayside magnetosphere. termination and Control System (ADCS), and 5) Or- Objective 3) Determine the flux, energy spectra, and spatial distribution of energetic neutral atoms bital Propulsion System (PROP). escaping from Jupiter’s magnetosphere. Jupiter’s The baseline JUMPER payload will carry two ion moon Io provides a 1-2 ton/s source of neutral material sensors, a magnetometer, and an ENA sensor. This to the jovian magnetosphere that is redistributed into a nominal payload will be based on high heritage in- neutral cloud around the moon’s orbit and is ultimately struments that can be or have been scaled to fit the lost from the system. As these neutrals become ionized SmallSat envelope while providing the high quality to form the Io plasma torus, an estimated 1/3 of the ion, magnetic field and ENA measurements needed to ions are transported outward to Jupiter’s plasma sheet address the JUMPER science objectives. while 1/3 – 1/2 of them are expected to escape as fast neutrals [16]. These fast neutrals are produced from References two sources: (i) charge exchange between inward- [1] Smith E. J. et al. (1978) JGR, 83, 4733. [2] diffusing energetic (> 10 keV/nucleon) ions and the Cowley S. W. H. et al. (2003), GRL, 30, 5. [3] McCo- extended H2 neutral cloud near Europa’s orbit and (ii) mas D. J., and Bagenal F. (2007), GRL, 34, L20106. charge exchange between the < 1 keV ions in the Io’s [4] Delamere P. A. and Bagenal F. (2010), GRL, 115, plasma torus and Io’s neutral cloud. The estimate loss A10201. [5] Clarke J. T. et al. (2009), JGR, 114, rate for these fast or energetic neutral atoms (ENAs) is A05210. [6] Gurnett D. A. et al. (2002), Nature, 415, ~ 0.3 – 1.7 tons/s [16] although direct measurement of 6875. [7] Hess S. L. G. et al. (2014), P&SS, 99, 136. these particles are needed to verify these values. One [8] Kivelson M. G. and Khurana K. K. (2002), JGR, approach is to remotely measure the distribution of 107, A8, SMP 23-1. [9] Jackman C. M. and Arridge C. ENAs emitted from the magnetosphere. Unfortunately, S. (2011), SoPh, 274, 1-2, 481 – 502. [10] Ebert R. W. only a very limited number of ENA observations from et al. (2014), FSPAS, 1, 4. [11] Huddlestron D. E. et Jupiter’s magnetosphere have been made [17] and al. (1997), JGR, 102, A11, 24289. [12] Sonnerup B. U. none at energies below 10 keV. O. et al. (1981), JGR, 86, 3321. [13] Walker R. J. and JUMPER will address this topic by remotely meas- Russel C. T. (1985), JGR, 90, 7397. [14] Ebert R. W. uring the flux, energy spectra, and spatial distribution et al. (2017), GRL, submitted. [15] Delamere P. et al. of ~0.5 – 10 keV ENAs from a vantage point on the (2015), SSRv, 187, 1 – 4, 51. [16] Bagenal F. and dayside of Jupiter’s outer magnetosphere. These meas- Delamere P. A. (2011), JGR, 116, A5. [17] Mitchell D. urements, coupled with physical chemistry [18] and G. et al. (2004), JGR, 109, A9. [18] Delamere P. A. et neutral transport [19, 20] models, will provide new al. (2004), JGR, 109, A10. [19] Smyth W. H. and Mar- insight on the physical processes that produce the fast coni M. (2005), Icarus, 176, 138-154. [20] Smyth W. neutrals in Jupiter’s inner magnetosphere and help H. and Marconi M. L. (2006), Icarus, 181, 510 – 526. constraint their contribution to the mass budget of Ju-

piter’s magnetosphere.