Miniaturised Instrumentation for the Detection of Biosignatures in Ocean Worlds of the Solar System

This review of miniaturised instrumentation is motivated by the ongoing and forthcoming exploration of the confirmed, or candidate ocean worlds of the Solar System. It begins with a section on the evolution of instrumentation itself, ranging from the early efforts up to the current rich-heritage miniaturised mass spectrometers approved for missions to the Jovian system. The geochemistry of sulphur stable isotopes was introduced for life detection at the beginning of the present century. Miniaturised instruments allow the measurement of geochemical biosignatures with their underlying biogenic coding, which are more robust after death than cellular organic molecules. The role of known stable sulphur isotope fractionation by sulphate-reducing bacteria is discussed. Habitable ocean worlds are discussed, beginning with analogies from the first ocean world known in the Solar System that has always being available for scientific exploration, our own. Instrumentation can allow the search for biosignatures, not only on the icy Galilean moons, but also beyond. Observed sulphur fractionation on Earth suggests a testable “Sulphur Hypothesis”, namely throughout the Solar System chemoautotrophy, past or present, has left, or are leaving biosignatures codified in sulphur fractionations. A preliminary feasible test is provided with a discussion of a previously formulated “Sulphur Dilemma”: It was the Galileo mission that forced it upon us, when the Europan sulphur patches of non-ice surficial elements were discovered. Biogenic fractionations up to and beyond δ34S = −70‰ denote biogenic, rather than inorganic processes, which are measurable with the available high sensitivity miniaturised mass spectrometers. Finally, we comment on the long-term exploration of ocean worlds in the neighbourhood of the gas and ice giants.

JANUS: the camera system onboard JUICE. Operational approach and scientific capabilities from operations case studies.

<p>The JUICE (JUpiter ICy moons Explorer) mission was selected in May 2012 as the first Large mission (L1) in the frame of the ESA Cosmic Vision 2015-2025 program and it will be launched in 2022. The mission aims to perform an in-depth characterization of the Jovian system, with an operational phase of about 3.5 years [1]. Main targets for this mission will be the vast Jovian system, including Jupiter itself, its magnetosphere, satellites, rings, neutral gas tori and the complex interplays among all those system components. Detailed investigations of three of Jupiter's Galilean icy satellites (Ganymede, Europa, and Callisto) will be achieved thanks to a large number of fly-bys and 9 months in orbit around Ganymede.</p> <p>JANUS (Jovis, Amorum ac Natorum Undique Scrutator) is the scientific camera system onboard JUICE [2]. Despite the resource limitations, and the environmental constraints, the instrument architecture and design will be able to satisfy the great variability of observing conditions for its different targets, benefiting from the spacecraft and orbit design to its maximum. The JANUS design has to cope with a wide range of targets, from Jupiter’s atmosphere, to solid satellite surfaces and their exospheres, rings, and transient phenomena like lightning. In order to obtain multispectral observations of scientific targets as well as specific observations in narrow bands, JANUS is equipped with a filter wheel mechanism with 13 wide and narrow-band filters, allowing wavelength coverage in the 340 - 1080 nm range. JANUS will greatly improve spatial coverage, resolution and time coverage on many targets in the Jupiter system. JANUS ground sampling ranges from 400 m/pixel to < 3 m/pixel for the three main Galilean satellites, and from few to few tens of km/pixel for Jupiter and other targets in the Jovian system, such as Io, the minor inner and outer irregular moons, and Jupiter’s rings. JANUS observations of Jupiter’s atmosphere will range from full mapping to regional imaging at spatial resolutions down to 10 km/pix. Global wind fields with accuracies better than 1.0 m/s will be obtained several times during the mission.</p> <p>Assuming the availability of scientific data volume (during operations about 20% of 1.4 Gbit/day is allocated to JANUS), JANUS observations will fully cover Ganymede in 4 colours with a resolution of about 100 m/pix as a goal, also providing regional DTMs. About 3% of the surface of Ganymede will be covered with a resolution of 10 - 30 m/pix for selected Regions of Interest, using both panchromatic and colour filters, and providing stereo images for the 3D reconstruction of the surface. This will represent dramatic improvements in imaging with respect to Galileo coverage in all the science targets covered by JUICE/JANUS.</p> <p>In addition to presenting the science goals that we are aiming to achieve during the JUICE science phase, we will show examples of a case study of operations, to highlight how the achievement of science goals is strictly related to the resources available to the instrument.</p> <p>References: [1] Grasset et al., (2013), <em>PSS, </em>78, 1-21. [2] Palumbo et al., (2014), <em>EGU conference</em></p> <p>Acknowledgements: The activity has been realized under the ASI-INAF contract 2018-25-HH.0. LML acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa” award to the Instituto de Astrofısica de Andalucia (SEV-2017-0709) and from project PGC2018-099425-B-I00 (MCI/AEI/FEDER, UE).</p>

Survey of Jupiter’s Plasma Disk from Juno Observations

<p>Using 30 inbound passes through the Jovian system, we combine measurements from the fields and particles instruments on the Juno spacecraft to survey the properties of Jupiter's plasma disk. Juno's orbit is particularly useful for exploring the variation in plasma conditions with latitude as well as radial distance (from ~10 to ~50 RJ). We present basic plasma properties (composition, density, temperature, velocity, magnetic field strength) to make maps of the plasma environment. Also show that on some of the 53-day orbits the plasma sheet has regular structure (density having roughly Gaussian distribution with latitude and decreasing with distance) but there are also highly irregular orbits with low or erratic density distributions.</p>

Connecting Jupiter's Auroral Pulsations with In-situ Measurements by Juno

<p><strong>In 1979, the Voyager spacecraft arrived at Jupiter. Amongst their rich array of discoveries, they identified bright bursts of radio emission at kHz frequencies</strong><sup>1</sup><strong>, often called quasi-periodic (QP) bursts, and discovered Jupiter’s ultraviolet (UV) aurora</strong><sup>2</sup><strong> - the most powerful aurora in the Solar System</strong><sup>3</sup><strong>. The same year that the Voyager spacecraft explored the Jovian system, the Einstein X-ray Observatory took the first X-ray images of Jupiter</strong><sup>4</sup><strong> and discovered that planets can also produce bright and dynamic X-ray aurora</strong><sup>5,6</sup><strong>. Over the subsequent decades, these distinct multi-waveband emissions have all been observed to pulse with quasi-periodic regularity</strong><sup>7–10</sup><strong>. Here, we combine simultaneous observations by the Juno spacecraft with the X-ray and UV observatories: XMM-Newton, Chandra and the Hubble Space Telescope. These observations show that the radio, UV and X-ray pulses are all synchronised, beating in time together. Further, they reveal that the X-ray and radio pulses share an identical 42.5 minute periodicity with simultaneously measured compression-mode Ultra Low Frequency (ULF) waves in Jupiter’s outer magnetosphere</strong><sup>11</sup><strong>. ULF waves are known to modulate wave-particle interactions that can cause electron and ion precipitation, providing a physically consistent explanation for the observed simultaneous ion and electron emissions.  The unification of Jupiter’s X-ray, UV and radio pulsations and their connection to ULF waves provides fundamental and potentially universal insights into the redistribution of energy in magnetised space environments.</strong></p>

The RADiation hard Electron Monitor (RADEM) for the JUICE mission

<p>The JUpiter ICy moons Explorer (JUICE) is the European Space Agency (ESA) next large class mission to the Jovian system. The mission, scheduled to launch in 2022, will investigate Jupiter and characterize its icy moons, Callisto, Europa and Ganymede for a period of 3.5 years after a 7.5-year cruise to the planet. JUICE is planned to flyby Europa and Callisto, perform a high latitude tour of the Jovian system, and finally, at the end of the mission, it will orbit Ganymede at different altitudes inside the moon’s intrinsic magnetosphere.<br /><br />While radiation is one of the major threats for all Space missions, in the Jovian system this problem is exacerbated due to the existent of very large fluxes of energetic electrons, with energies up to dozens of MeV, which can damage and eventually destroy the spacecraft systems. The existence of this electron population, and to a lesser extent of a proton and heavy ion population, is a consequence of Jupiter’s huge magnetosphere which can accelerate these particles to energies higher than those found in other known planetary magnetospheres. Although the Galileo mission, and to a lesser extent the Cassini, Pioneer and Voyager missions have provided ample information about the radiation environment in the Jovian, several questions about particle origin, acceleration mechanisms, Jovian-Solar magnetosphere coupling, and overall dynamics of the system still need to be answered with implications in magnetospheric physics, astrobiology and others, as well as in development of future manned and unmanned missions to both the inner and outer Solar System.<br /><br />For these reasons, the JUICE mission will include the RADiation hard Electron Monitor (RADEM), a low power, low mass radiation monitor, that will increase the range of long-term spectral measurements acquired by the Energetic Particle Detector (EPD) aboard the Galileo spacecraft, from 11 to 40 MeV for electrons and from 55 to 250 MeV for protons. RADEM consists of three detector heads based on traditional silicon stack detector technologies: the Electron Detector Head (EDH), the Proton Detector Head (PDH), and the Heavy Ion Detector Head (HIDH), that will measure electrons from 0.3 MeV to 40 MeV, protons from 5 MeV to 250 MeV and Heavy Ions from Helium to Oxygen with energies from 8 to 670 MeV, respectively. Because the detectors have limited Field-Of-View, a fourth detector, the Directionality Detector Head (DDH) will measure electron angular distributions which can vary greatly along the Jovian System as observed by the Galileo spacecraft.<br /><br />Although RADEM is a housekeeping instrument that will provide in-situ Total Ionizing Dose (TID) measurements and serve as a radiation level alarm, it has a broad scientific potential. Besides the Jovian system, the instrument will be fully operated during the cruise of the Solar System, which includes three Earth flybys, a Venus flyby and a Mars flyby, that offer additional scientific opportunities including but not limited to studying the cosmic ray gradient in the Solar System, characterizing Solar Energetic Particle (SEP) events, and others. In this work, we will present RADEM from a technical point-of-view, as well as the scientific opportunities that will be addressed by the radiation monitor during the JUICE mission.</p>

Recent results from the imagery of Juno’s Stellar Reference Unit

<p>The Juno Mission has recast its spacecraft engineering star camera as a visible wavelength science imager. Developed and primarily used to support onboard attitude determination, Juno’s Stellar Reference Unit (SRU) has been put to use as an in situ high energy particle detector for profiling Jupiter’s radiation belts and as a low light sensitive camera for exploring multiple phenomena and features of the Jovian system. Juno’s unprecedented polar orbit and closest approach of ~4000 km have yielded high resolution SRU imagery of Jupiter’s lightning and aurorae from as little as 50,000 km from the 1 bar level and unique Jovian dust ring and satellite images. We will present recent SRU results and discuss the implications for Jupiter’s atmosphere that stem from the SRU lightning observations.</p>

Vectorized magnetometer for space applications using electrical readout of atomic scale defects in silicon carbide

Magnetometers are essential for scientific investigation of planetary bodies and are therefore ubiquitous on missions in space. Fluxgate and optically pumped atomic gas based magnetometers are typically flown because of their proven performance, reliability, and ability to adhere to the strict requirements associated with space missions. However, their complexity, size, and cost prevent their applicability in smaller missions involving cubesats. Conventional solid-state based magnetometers pose a viable solution, though many are prone to radiation damage and plagued with temperature instabilities. In this work, we report on the development of a new self-calibrating, solid-state based magnetometer which measures magnetic field induced changes in current within a SiC pn junction caused by the interaction of external magnetic fields with the atomic scale defects intrinsic to the semiconductor. Unlike heritage designs, the magnetometer does not require inductive sensing elements, high frequency radio, and/or optical circuitry and can be made significantly more compact and lightweight, thus enabling missions leveraging swarms of cubesats capable of science returns not possible with a single large-scale satellite. Additionally, the robustness of the SiC semiconductor allows for operation in extreme conditions such as the hot Venusian surface and the high radiation environment of the Jovian system.