Table 3.
Ganymede
| Objectives | Investigations | Measurement Requirements | Instruments | |
|---|---|---|---|---|
| Characterise the extent of the ocean and its relation to the deeper interior. | GA.1 | Determine the amplitude and phase of the gravitational tides. | GA.1a. Measure spacecraft acceleration to resolve 2nd degree gravity field time dependence. Recover k2 at the orbital frequency of Ganymede with an accuracy of 5⋅10−4 (real) or 1⋅10−3 (complex) by performing range-rate measurements (accuracy ∼0.01 mm/s at 60 sec integration time) to determine spacecraft orbit to better than 1-meter (rms) over several tidal cycles. Determine the position of Ganymede’s center of mass relative to Jupiter during the lifetime of the mission to better than 10 meters, by performing range measurements with an accuracy of 20 cm end-to-end and range-rate measurements (accuracy ∼0.01 mm/s at 60 sec integration time) to determine spacecraft orbit to better than 1-meter (rms) throughout the lifetime of the orbiter. | 3GM |
| GA.1b. Measure topographic differences from globally distributed repeat ranging measurements, to recover spacecraft altitude at crossover points to 1-meter vertical accuracy by contiguous global ranging to the surface with 10-cm accuracy. | GALA | |||
| GA.2 | Characterise the space plasma environment to determine the magnetic induction response from the ocean. | GA.2a. Measure three-axis magnetic field components (at 32 to 128 Hz with a resolution of 0.1 nT) over a range of orbital phases to determine the induction response at multiple frequencies (related to satellite orbital and Jupiter rotation time scales). | JMAG | |
| GA.2b. Determine the distribution functions for electrons and ions (first order mass resolution) with an angular and energy coverage sufficient to determine the cold plasma density and velocity to constrain contributions from currents not related to the surface and ocean. Identify open and closed field lines with a latitudinal accuracy of ≤1° in Ganymede circular orbit by measuring electrons in opposing directions with a time resolution of ≤20 s. | PEP | |||
| GA.2c. Measure electric field vectors at DC to 1.6 MHz better than <1 mV/m accuracy. Measure the vector magnetic field variations at 0.1 Hz–20 kHz. Together with electron and ion density (10−4 to 105 /cm3) measurements with better than 20% accuracy, determine conductivity and electrical currents. Measure electron temperature (0.01–100 eV) and the ion drift speed (<200 km/s). | RPWI | |||
| GA.3 | Characterise surface motion over Ganymede’s tidal cycle. | GA.3a. Measure topographic differences (tidal amplitudes) with respect to the reference ellipsoid from globally distributed repeat measurements at varying orbital phase, with better than or equal to 1-meter vertical accuracy, to recover h2 to 0.01 (at the orbital frequency) by contiguous global ranging to the surface with 10-cm accuracy. | GALA | |
| GA.3b. Measure spacecraft acceleration to resolve the position of the spacecraft to better than 1-meter (rms) by performing range-rate measurements with an accuracy ∼0.01 mm/s at 60 sec integration time to determine spacecraft orbit to better than 1-meter (rms) over several tidal cycles. | 3GM | |||
| GA.3c. Provide supplementary measurements of the S/C differential lateral position relative to the ICRF2 background extragalactic radio sources with the accuracy of 100–10 μas (1 sigma) over integration time 60–1000 s. | PRIDE | |||
| GA.4 | Determine the satellite’s dynamical rotation state (forced libration, obliquity and nutation). | GA.4a. Determine the amplitude of physical longitudinal librations and the orientation of the spin pole by determining surface elevations and the orientation of the global shape at varying orbital phase of Ganymede (different true anomalies with respect to Jupiter), with up to 1-meter vertical accuracy, short along-track distance between the laser spots (few tens of meters) and by taking continuous tracks. | GALA | |
| GA.4b. Acquire multiple images of the same surface target at varying orbital phase, to determine satellite’s surface relative rotational position with better than 10 m horizontal accuracy. This would allow an independent evaluation of the mean spin pole, the forced nutation of the spin pole and the amplitude of the forced libration of Ganymede’s surface through fitting data with rotation models. | JANUS | |||
| GA.4c. Perform range measurements with an accuracy of 20 cm end-to-end and range-rate measurements (accuracy ∼0.01 mm/s at 60 sec integration time) to a) determine the spacecraft position during circular orbits with an accuracy < 10 cm radial, < 10 m along track, <10 m (1–2 meters) out of plane (orbital frame of reference), to provide the appropriate referencing to laser altimeter measurements and optical imaging; and b) determine Ganymede’s physical librations in longitude and pole position in the putative body-fixed frame to accuracies about 10–20 m. | 3 GM | |||
| GA.5 | Investigate the core and rocky mantle. | GA.5a. Resolve the gravity field to degree and order 12 or better by performing range-rate measurements (accuracy ∼0.01 mm/s at 60 sec integration time) to determine spacecraft orbit to better than 1-meter (rms). | 3GM | |
| GA.5b. Perform topographic measurements to resolve coherence with gravity to degree and order 12 or better, with better than or equal to 1-meter vertical accuracy, by contiguous global ranging to the surface with 10-cm accuracy. | GALA | |||
| GA.5c. Measure three-axis magnetic field components (at 32 to 128 Hz with a resolution of 0.1 nT) to determine whether there is a induction response at the Jupiter rotation rate. | JMAG | |||
| GA.5d. Perform astrometric determination of the rate of change of Ganymede’s orbit by acquiring multiple images of the moon from a distance including background stars with a position accuracy of at least 1 km. | JANUS | |||
| GA.5e. Provide supplementary measurements of the S/C differential lateral position relative to the ICRF2 background extragalactic radio sources with the accuracy of 100–10 μas (1 sigma) over integration time 60–1000 s. | PRIDE | |||
| Characterise the ice shell. | GB.1 | Characterise the structure of the icy shell including its properties and the distribution of any shallow subsurface water. | GB.1a Obtain profiles of subsurface thermal, compositional and structural horizons down to a few kilometers (maximum depth from 1 to 9 km depending on the crust properties), with better than 50-km profile spacing, and with vertical resolution ranging from ∼50 meters to 1% of the target depth; Estimate subsurface dielectric properties and the density of buried scatterers in targeted regions. | RIME |
| GB.1b. Obtain topography with a few tens of meters along-track resolution and better than or equal to 1 meter vertical accuracy. The maximum distance between ground-tracks (usually obtained in equatorial regions because of the polar orbit) shall be less than 5 km (goal: a few hundred meters). Determine surface roughness on the scale of 50 m or better from the laser return pulse. | GALA | |||
| GB.2 | Correlate surface features and subsurface structure to investigate near-surface and interior processes. | GB.2a. Subsurface sounding: maximum depth from 1 to 9 km depending on the crust properties), with better than 50-km profile spacing, and with vertical resolution ranging from ∼50 meters to 1% of the target depth, in order to:- Obtain profiles of subsurface dielectric horizons and structures down to a few kms - Estimate subsurface dielectric properties and the density of buried scatterers in targeted regions.- Perform globally distributed profiling of subsurface thermal, compositional and structural horizons down to a few kms.- Determine the thermal emission flux by identifying thermally-controlled subsurface horizons within the ice shell | RIME | |
| GB.2b. Measure topography at better than or equal to 1-km horizontal scale, better than or equal to 5-meter vertical resolution and with a few tens of meters along-track resolution, over the areas co-located with subsurface profiles sounding data. | GALA | |||
| GB.2c. Measure surface reflectance in the wavelength range from 0.4 to greater than or equal to 5 microns of targeted features at better than or equal to 125 m/px spatial resolution, with spectral resolution sufficient to distinguish sulfuric acid hydrate from Mg- and Na-enriched salt hydrates; better than 5 nm from 0.4 to 2.0 microns and better than 10 nm from 2.0 to greater than or equal to 5 microns). | MAJIS | |||
| GB.2d. Measure surface reflectance in the wavelength range from 0.1 to 0.2 microns of targeted features at better than or equal to 1 km/px spatial resolution, with < 2 nm from 0.1 to 0.2 microns. | UVS | |||
| GB.2e. Perform radiometric-polarized measurements in the 600 GHz band with spatial resolution of at least 5 km and under different off-nadir angles in order to constrain the thermophysical properties of the ice, regolith and ice-regolith mixtures down to a few cm. Determine the thermal emission flux by measuring global surface thermal emission at a spatial resolution of at least 10 km/px. | SWI | |||
| GB.2f. Perform detailed three-dimensional surface morphological characterization of targeted features through imaging at better than or equal to 30-meter horizontal scale and 15-meter vertical accuracy across selected targets. For generation of DTM for RIME data interpretation, measure topography along subsurface profiles with horizontal resolution better than 300 m/px and vertical resolution better than 50 m. | JANUS | |||
| Characterise the local environment and its interaction with the jovian magnetosphere. | GC.1 | Globally characterise Ganymede’s intrinsic and induced magnetic fields, with implications for the deep interior. | GC.1a. Measure three-axis magnetic field components at 32 to 128 Hz with a resolution of 0.1 nT. | JMAG |
| GC.1b. Determine the distribution functions for electrons and ions (first order mass resolution) with an angular and energy coverage sufficient to determine the cold plasma density and velocity to constrain contributions from currents not related to the surface and ocean. Determine the particle precipitation pattern by imaging the backscattered neutrals in Ganymede Circular Orbit in the tens eV to few keV range with an angular resolution ≤7°. Identify the open-closed field line boundary and its variability with an latitudinal accuracy of ≤1° in Ganymede circular orbit by measuring electrons in opposing directions with a time resolution of ≤20 s. | PEP | |||
| GC.1c. Measure electric field vectors at DC to 1.6 MHz better than <1 mV/m accuracy. Measure the vector magnetic field variations at 0.1 Hz-20 kHz. Together with electron and ion density (10−4 to 105 /cm3) measurements with better than 20% accuracy, determine conductivity and electrical currents. Measure electron temperature (0.01-100 eV) and the ion drift speed (0.1–200 km/s). | RPWI | |||
| GC.2 | Characterise the particle population within Ganymede’s magnetosphere and its interaction with Jupiter’s magnetosphere. | GC.2a. Measure three-axis magnetic field components at 32 to 128 Hz with a resolution of 0.1 nT. | JMAG | |
| GC.2b. Measure the distribution of bulk plasma and bulk ion drift speed with 10 second resolution; Determine electron and ion density 10−4–105/cm3, electron temperature (0.01- to 100-eV), bulk ion drift speed (<200 km/s), as well as suprathermal electrons (non-Maxwellian distribution). Constrain ion temperature (0.02 to 20 eV). The acceleration of particles by Alfvén- and plasma waves requires electric field vector (DC-1.6 MHz), density fluctuations (δn/n, DC-10 kHz) and magnetic field vector (0.1–20 kHz) measurements, and monitoring of radio waves (80 kHz–45 MHz). | RPWI | |||
| GC.2c. Determine the distribution functions of electrons and ions with a sufficient angular and energy coverage to derive the moments (density, velocity, pressure) with a 10 second resolution and first order mass analysis. Determine plasma composition with the mass resolution M/ΔM greater than 20. Measure the volatile content of the exosphere, over a mass range better than 300 Daltons, mass resolution better than 500. Determine the particle precipitation pattern by imaging the backscattered neutrals in Ganymede Circular Orbit in the tens eV to few keV range with an angular resolution ≤7°. | PEP | |||
| GC.2d. Measure Ganymede’s aurora emissions with sufficient spatial resolution to characterise the variability of the atmosphere and provide a complementary observation of the open/closed field line boundary through two-dimensional spectral-spatial images. Perform observations in the wavelength range of 120- to 200-nm to measure OI (135.6 nm, 130.4 nm) and H Ly alpha with a spectral resolution of at least 2 nm to derive information on the energy and energy flux of the incoming particles. | UVS | |||
| GC.3 | Investigate the generation of Ganymede’s aurorae. | GC.3a. Determine the distribution functions of electrons and ions with a sufficient angular and energy coverage to derive the moments (density, velocity, pressure) with a 10 second resolution and first order mass analysis. Determine the spatial-temporal variability of particle precipitation by imaging the backscattered neutrals in Ganymede Circular Orbit in the tens of eV to few keV range with an angular resolution ≤7°. Determine the variable Jovian magnetospheric environment local to Ganymede by imaging ENAs in the 10-100’s keV range produced with an angular resolution ≤10° (first order mass resolution) with a time resolution of 1 h. Measure the volatile content of the exosphere, over a mass range better than 300 Daltons, mass resolution better than 500. | PEP | |
| GC.3b. Measure three-axis magnetic field components at 32 Hz (required rate depends on the expected orbital velocity such that the magnetic field vector is sampled at least once per 300 km). | JMAG | |||
| GC.3c. Perform multi-wavelength spectral and monochromatic imaging of Ganymede’s aurora in the wavelength range of 120-200 nm with a spectral resolution of ≤2 nm. Requires a temporal resolution of 1-minute and a spatial resolution ≤2.6-km/px. | UVS | |||
| GC.3d. Perform multi-wavelength spectral and monochromatic imaging of Ganymede’s aurora in the wavelength range from 0.4 to at least 5 microns with a spectral resolution of better than or equal to 5 nm from 0.4 to 2 mm; better than or equal to 10 nm from 2 to at least 5 mm; Requires a temporal resolution of 1-minute and a spatial resolution better than 1 km/x. | MAJIS | |||
| GC.3e. Measure electric field vectors/polarization (DC to 45 MHz), including electrostatic acceleration structures. Determine electron and ion density (10−4–105/cm3), bulk ion drift speed (<200 km/s), as well as suprathermal electrons. Measure small scale density perturbations (δn/n, DC to 10 kHz). Determine the presence of electrostatic and electromagnetic wave emissions of importance for the auroral energy transfer (DC to 20 kHz). Measure radio waves from auroral acceleration regions (1 kHz-45 MHz). | RPWI | |||
| GC.4 | Determine the sources and sinks of the ionosphere and exosphere. | GC.4a. Obtain two-dimensional spectral-spatial images in the wavelength range of 120 to 200 nm to determine column densities of atmospheric species at better than or equal to 1 km/px spatial resolution. Spectral resolution: ≤ 1 nm from 120 to 200 nm;Perform long-term and high-temporal-resolution monitoring in context of magnetospheric variations. Determine the composition, distribution and physical characteristics (grain-size, crystallinity, physical state) of volatile materials on the surface in the spectral range 100 –200 nm, including potential measurements of water ice, O2, O3, H2O2, carbon dioxide ices and other species. Spectral resolution: better than or equal to 2 nm. Perform stellar occultations in the wavelength range from 100 nm to 200 nm to search for absorption and/or emission signatures of atmospheric species (e.g., H2O, O2). Cover 100 to 200 nm at ≤ 1 nm resolution, and latitude and longitude resolution of ≤ 30°. Perform scans perpendicular to the limb from ∼5 km above the surface to the surface of the satellite in the wavelength range of 100–200 nm with spectral resolution of 2 nm to measure or search for emission from O (135.6 nm) and other species in the atmosphere. | UVS | |
| GC.4b. Obtain two-dimensional spectral-spatial images in the wavelength range of 0.4- to 5-microns to determine column densities of atmospheric species at better than or equal to 1 km/px spatial resolution. Spectral resolution: better than or equal to 5 nm from 0.4 to 2 μm; better than or equal to 10 nm from 2 to at least 5 μm. Perform long-term and high-temporal-resolution monitoring in context of magnetospheric variations. Determine the composition, distribution and physical characteristics (grain-size, crystallinity, physical state) of volatile materials on the surface in the spectral range 1–5 microns, including measurements of water ice, O2, O3, H2O2, carbon dioxide ices and other species. Spectral resolution: better than or equal to 10 nm. Perform stellar occultations in the wavelength range from 0.4 to 5.0 microns to search for absorption and/or emission signatures of atmospheric species (e.g., water and oxygen). Perform scans perpendicular to the limb from ∼5 km above the surface to the surface of the satellite in the wavelength range of 1.0 to 5.0 microns (spectral resolution better than or equal to 5 nm from 1.0 to 2.0 microns and better than or equal to 10 nm from 2.0 to greater than or equal to 5.0 microns) to measure or search for emission from O2 (1.27 microns), H2O, CO2 (4.26 microns) and other species in the atmosphere. | MAJIS | |||
| GC.4c. Determination of the oxygen and hydrogen isotopic composition of surface water ice along sub-solar longitudes at about 5 km spatial resolution through observations in the 600 GHz band. Determine the vertical temperature profile from the ground up to at least 200-km altitude with about 5 km vertical resolution by measurement of and in the 600 GHz band. Determine the distribution of water vapour from water line observations in the 600 GHz band. | SWI | |||
| GC.4d. Perform radio occultations to measure the neutral atmosphere and ionosphere. | 3GM | |||
| GC.4e. Measure neutrals coming off Ganymede with a mass range up to 300 Daltons and a mass resolution of up to 500. Determine the distribution functions of electrons and ions with a sufficient angular and energy coverage to derive the moments (density, velocity) with a 10 second resolution and mass resolution sufficient to distinguish between key magnetospheric and ionospheric pickup ions. Measure neutral exospheric composition with sufficient accuracy and to sufficient mass resolution to identify major volatile species with mixing ratios better than 1%. Determine the particle precipitation zones by imaging the sputtered and backscattered neutrals from the surface in the 10’s eV to few keV range with an energy resolution ≤100% and angular resolution ≤7°. | PEP | |||
| GC.4f. Measure three-axis magnetic field components at 32 to 128 Hz with a resolution of 0.1 nT. | JMAG | |||
| GC.4g. Determine the plasma density and temperature of the ionosphere, ion drift speeds (dynamics) in the ionosphere, and the electric field vector with accuracy better than 0.1 mV/m. Measure electron and ion density (10−4–105/cm3) and electron temperature (0.01–100 eV), as well as the ion ram speed (<200-km/s). Constrain ion temperature (0- to 20- eV). Determine the ionizing Extreme Ultraviolet flux. Determine the electric field vectors (near DC to 1.6 MHz). Determine the presence of suprathermal electrons and plasma inhomogenities (δn/n, 0–10 kHz). Determine energy transport by Alfvén- and plasma waves between populations, by measuring the electric (DC-45 MHz) and magnetic field (0.1 Hz–20 kHz) vectors. Monitor cut-off frequencies with distance from Ganymede of natural Jovian radio emissions (80 kHz-45 MHz). | RPWI | |||
| GC.4h. Provide supplementary multi-static measurements of occultation radio signal for characterisation of the ionosphere and neutral atmosphere. | PRIDE | |||
| Understand the formation of surface features and search for past and present activity. | GD.1 | Determine the formation mechanisms and characteristics of magmatic, tectonic, and impact landforms. | GD.1a. Determine the distributions and morphologies of surface landforms at regional and local scales. Constrain the regional and global stratigraphic relationships among landforms by determining surface color characteristics at ∼100 m/px scale in at least 3 colors with near-uniform lighting conditions and solar phase angles less than or equal to 45 degrees. Characterise selected 20-km x 20-km (or larger) areas at 10 m/px. Characterise small-scale three-dimensional surface morphology, at better than 10 m/px over targeted sites, with vertical resolution of better than or equal to 5-meter (1-meter as a goal). Requires context coverage at 10x bigger scale and not worse than 10x coarser resolution. Globally characterise the morphology at least at a spatial resolution of 400 m/px (desired 100 m/px) to provide context for higher resolution data. | JANUS |
| GD.1b. Altimetric profiles over targeted sites to at least 5 meter vertical resolution and a few tens of meters along-track resolution between ground-spots. The distance between different tracks shall be less than 1 km horizontal resolution (goal: a few hundred meters). | GALA | |||
| GD.1c. Obtain profiles of subsurface dielectric horizons and structures down to a few kilometers (maximum depth from 1 to 9 km depending on the crust properties), with better than 50-km profile spacing, and with vertical resolution ranging from ∼50 meters to ∼1% of the target depth; Estimate subsurface dielectric properties and the density of buried scatters in targeted regions. | RIME | |||
| GD.2 | Constrain global and regional surface ages. | GD.2a. Determine the distributions and morphologies of surface landforms at regional and local scales. Constrain the regional and global stratigraphic relationships among landforms by imaging at ∼100 m/px in at least 3 colors with near-uniform lighting conditions and solar phase angles less than or equal to 45 degrees. Characterise the morphology of targeted features through imaging at better than 10 m/px spatial scale. | JANUS | |
| GD.2b. Acquire high spatial resolution observations (better than or equal to 125 m/px) from 0.4 to 5.0 microns (spectral resolution: better than or equal to 5 nm from 400 nm to 2.0 microns; better than or equal to 10 nm from 2.0 to greater than or equal to 5 microns) on the leading hemisphere, particularly on the subjovian quadrant, with emphasis on the spectral differences between geologic features and the surrounding areas. Medium spatial resolution (2.5–10 km/px) on large areas to map leading/trailing asymmetries due to contamination by exogenic material. | MAJIS | |||
| GD.2c. Acquire high spatial resolution observations (≤ 1 km/px) from 100 nm to 200 nm (spectral resolution: ≤ 2 nm from 100 to 200 nm) on the leading hemisphere, particularly on the subjovian quadrant, with emphasis on the spectral differences and slopes between geologic features and the surrounding areas. Medium spatial resolution (≤ 5 km/px) on large areas to map leading/trailing asymmetries due to contamination by exogenic material. | UVS | |||
| GD.2d. Globally identify and locally characterize physical and dielectric subsurface horizons down to a few kms, (maximum depth from 1 to 9 km depending on the crust properties with vertical resolution ranging from a minimum of ∼50 meters to 1% of the target depth) by obtaining subsurface sounding profiles with better than 50 km spacing. | RIME | |||
| GD.3 | Investigate processes of erosion and deposition and their effects on the physical properties of the surface. | GD.3a. Characterise the morphology of targeted features through imaging at better than 10 m/px spatial scale. | JANUS | |
| GD.3b. Determine the particle precipitation zones by measuring (in-situ) the precipitating electrons and ions (major magnetospheric species) in the 10’s eV to MeV energy range, and by imaging the sputtered and backscattered neutrals from the surface in the 10’s eV to few keV range with an energy resolution ≤100% and angular resolution ≤7°. Measure sputtered exospheric products over a mass range better than 300 Daltons, mass resolution better than 500. | PEP | |||
| GD.3c. Measure three-axis magnetic field components at 32 to 128 Hz and with a resolution of 0.1 nT to observe ion cyclotron waves; relate these waves to neutral ionization and plasma pickup in order to constrain sputtering rates. | JMAG | |||
| GD.3d. Measure the DC electric field vector (DC-1 kHz) to monitor electrostatic acceleration structures and Alfvén waves that accelerate charged particles toward surface. Determine charge level on dust population by measuring the electron and ion densities (10−4–105/cm3), and the spacecraft potential at +/−100 V at 1 V accuracy. | RPWI | |||
| GD.3e. Perform measurements in the wavelength range of 1 to 5 microns with a spectral resolution better than or equal to 5 nm to characterise water ice bands at 1650 nm, 2000 nm, 3100 nm and 4530 nm (e.g. grain size), and hydrated salts and sulfuric acid hydrate at a spatial resolution better than 1 km. | MAJIS | |||
| Determine global composition, distribution and evolution of surface materials. | GE.1 | Characterise surface organic and inorganic chemistry, including abundances and distributions of materials. | GE.1a. Identify and map non-water-ice materials (including organic compounds and radiolytic materials) over a wide range of spatial scales (from 5 km/px to 1 km/px or better), in the overall spectral range of 0.4 to greater than or equal to 5 microns and with a spectral resolution better than or equal to 5 nm from 400 nm to 2.0 microns and better than or equal to 10 nm from 2.0 to greater than or equal to 5 microns. At least 50% coverage with spatial resolution between 2 and 3 km/px. Identify globally distributed bulk material composition by measuring grain size, porosity, crystallinity, and physical state of water ice in the spectral range from 1.0 to 4.0 microns with a spectral resolution better than or equal to 10 nm and over a wide range of spatial scales (from 10 km/px to 100 m/px or better) and illumination conditions. | MAJIS |
| GE.1b. Identify and map non-water-ice materials (including organic compounds and radiolytic materials) over a wide range of spatial scales (from 5 km/px to 1 km/px or better), in the overall spectral range of 100 – 200 nm and with a spectral resolution of ≤ 2 nm. At least 50% coverage with spatial resolution ≤3 km/px. | UVS | |||
| GE.1c. Identify globally distributed bulk material composition by measuring grain size, porosity, crystallinity, and physical state of water ice from polarized continuum observations of the surface in the 600 GHz band under different off-nadir angles. | SWI | |||
| GE.1d. Constrain the dielectric permittivity of the surface material by bistatic radar observations. | 3GM | |||
| GE.1e. Image at resolution better than 10 m/px with an image width of ∼2 km. Obtain repeat coverage to facilitate stereo analysis of targeted features. | JANUS | |||
| GE.1f. Characterise the composition of sputtered surface products over a mass range better than 300 Daltons, mass resolution better than 500. Image the sputtered and backscattered neutrals from the surface in the 10’s eV to few keV range with an energy resolution ≤100% and angular resolution ≤7°. | PEP | |||
| GE.1g. Provide supplementary multi-static measurements of radio occultation radio signal for estimates of dielectric properties of the surface. | PRIDE | |||
| GE.2 | Relate compositions and properties and their distributions to geology. | GE.2a. Acquire global imaging at 400 m/px in four colors (e.g. 0.4, 0.5, 0.7, and 0.9 μm). Obtain three-color (e.g. 0.4, 0.7, 0.9 μm) and monochromatic coverage for selected large areas at up to or better than 100 m/px. Acquire image mosaics at a uniform spatial resolution and illumination angle (e.g. mid-morning/mid-afternoon). Characterise the morphology through imaging at better than 10 m/px spatial scale over regions of high interest. For generation of DTM for RIME data interpretation, measure topography along subsurface profiles with horizontal resolution better than 300 m/px and vertical resolution better than 50 m. | JANUS | |
| GE.2b. Identify surface modifications due to external plasma and particle interactions by measuring (in-situ) the precipitating electrons and ions (major magnetospheric species) in the 10’s eV to MeV energy range, and by imaging the sputtered and backscattered neutrals from the surface in the 10’s eV to few keV range with an energy resolution ≤100% and angular resolution ≤7°. Measure neutral exospheric composition with sufficient sensitivity and to sufficient mass resolution to identify major volatile species with mixing ratios better than 1%. | PEP | |||
| GE.2c. Detect dust and determine its mass and size distribution with electric field (DC to 45 MHz). Determine charge level on dust population by measuring the electron and ion densities (10−4–105/cm3), and the spacecraft potential at +/−100 V at 1 V accuracy. Measure the DC electric field vector (DC-1 kHz) to monitor electrostatic acceleration structures and Alfvén waves that accelerate charged particles toward surface. | RPWI | |||
| GE.2d. Identify and locally characterize subsurface compositional horizons and structures by obtaining profiles of subsurface dielectric horizons and structures (maximum depth from 1 to 9 km depending on the crust properties with vertical resolution ranging from a minimum of ∼50 meters to 1% of the target depth), with better than 50-km profile spacing; estimate subsurface dielectric properties and the density of buried scatterers in targeted regions. | RIME | |||
| GE.2e. Measure topography with at least 5 meter vertical resolution and a few tens of meters along-track resolution between ground-spots. The distance between different tracks shall be less than 1 km horizontal resolution (goal: a few hundred meters) over the areas co-located with subsurface profiles. | GALA | |||
| GE.2f. Map non-water-ice materials (including organics and products of radiolysis and ion bombardment, e.g. H2O2, O3, H2CO, H2CO3) and their association with known geologic features over the wavelength range of 100 nm to 200 nm with spectral resolution better than or equal to 2 nm. Requires at least 50% coverage with spatial resolution ≤3 km/px. | UVS | |||
| GE.2g. Map non-water-ice materials (including potential organics and products of radiolysis and ion bombardment, e.g. H2O2, O3, H2CO, H2CO3) and their association with known geologic features over the wavelength range of 400-nm to greater than or equal to 5.0 microns with spectral resolution better than or equal to 5 nm from 400 nm to 2.0 microns; better than or equal to 10 nm from 2.0 to greater than or equal to 5.0 microns. Requires at least 50% coverage with spatial resolution between 2 and 3 km/px. Determine the origin and evolution of non-water-ice materials by making measurements in the wavelength range from 0.4 to at least 5.0-microns with a spectral resolution better than or equal to 10 nm and a spatial resolution better than or equal to 125 m/px of representative features. Co-register with higher-resolution monochromatic images at better than or equal to 100 m/px (see GE.2a). | MAJIS | |||
| GE.3 | Investigate surface composition and structure on open vs. closed field line regions. | GE.3a. Map several known or expected tracer species of weathering effects induced by the magnetosphere (e.g., H2O, CO2, NH3, O3, H2O2, H2SO4 hydrate, etc.) over the wavelength range of 100 to 200 nm with spectral resolution ≤ 5 nm. Requires at least 50% coverage with spatial resolution ≤ 3 km/px. | UVS | |
| GE.3b. Map several known or expected tracer species of weathering effects induced by the magnetosphere (e.g., H2O, CO2, NH3, O3, H2O2, H2SO4 hydrate, etc.) over the wavelength range of 1.0 to 2.0 μm with a spectral resolution better than or equal to 5 nm and 2.0 to at least 5 μm with a spectral resolution less than or equal to 10 nm. Requires at least 50% coverage with spatial resolution between 2 and 3 km/px. Map the distribution of the state of water ice (crystalline vs. amorphous) as a function of the latitude, in the spectral range from 1.0- to 4.0-μm with spectral resolution less than or equal to 10 nm. Map targeted features to assess local conditions (albedo) in the 0.4- to 1.0-μm range. Requires at least 50% coverage with spatial resolution between 2 and 3 km/px. | MAJIS | |||
| GE.3c. Measure three-axis magnetic field components at 32 to 128 Hz and with a resolution of 0.1 nT at different orbital phases and distances less than 0.5 moon radii. | JMAG | |||
| GE.3d. Global monochromatic imaging at 400 m/px with selected features mapped in 4 colors (e.g. 0.4-μm, 0.5-μm, 0.7-μm, 0.9-μm) at 100 m/px. Targeted imaging at a resolution of better than 30 m/px over regions of interest. | JANUS | |||
| GE.3e. Identify open and closed field lines with an latitudinal accuracy of ≤1° in Ganymede circular orbit by measuring electrons in opposing directions with a time resolution of ≤20 s. Measure neutral exospheric composition with sufficient sensitivity and to sufficient mass resolution to identify major volatile species with mixing ratios better than 1%. Determine the particle precipitation zones by measuring (in-situ) the precipitating electrons and ions (major magnetospheric species) in the 10’s eV to MeV energy range, and by imaging the sputtered and backscattered neutrals from the surface in the 10’s eV to few keV range with an energy resolution ≤100% and angular resolution ≤7°. | PEP | |||
| GE.3f. Measure electron and ion density (10−4–105/cm3) and electron temperature (0 to 100 eV), as well as constrain ion temperature (0 to 20 eV) on open versus closed field lines. Determine charge level on dust population by measuring the electron and ion densities (10−4–105/cm3), and the spacecraft potential at +/−100 V at 1 V accuracy. Measure the DC electric field vector (DC-1 kHz) to monitor electrostatic acceleration structures and Alfvén waves that accelerate charged particles toward surface. | RPWI | |||
| GE.4 | Determine volatile content to constrain satellite origin and evolution. | GE.4a. Measure the stable isotopes of C, H, O, and N in the major volatiles (e.g. H2O, CH4, NH3, CO, CO2, SO2), and measure the noble gases Ar, Kr, and Xe, with mass resolution better than 500. Characterise the composition of sputtered desorbed volatiles over a mass range better than 300 Daltons with mass resolution better than 500. | PEP | |
| GE.4b. and the 17O/16O and 18O/16O ratio in water ice from limb observations of water rotational transitions in the 600 GHz band. Identify globally distributed bulk material composition from polarized continuum observations of the surface in the 600 GHz band under different off-nadir angles. | SWI | |||
| GE.4c. Identify and map non-water-ice materials over a wide range of spatial scales (from 5 km/px to 1 km/px or better), in the overall spectral range 0.1–0.2 micron and with a spectral resolution better than or equal to 2 nm, suitable to discriminate various volatiles known or expected to exist on the surface. Requires at least 50% coverage with spatial resolution ≤ 3 km/px. | UVS | |||
| GE.4d. Identify and map non-water-ice materials over a wide range of spatial scales (from 5 km/px to 1 km/px or better), in the overall spectral range 0.4 to greater than or equal to 5 μm and with a spectral resolution better than or equal to 5 nm from 0.4 to 2.0 μm and better than or equal to 10 nm from 2.0 to greater than or equal to 5 μm, suitable to discriminate various volatiles known or expected to exist on the surface. Requires at least 50% coverage with spatial resolution between 2 and 3 km/px. Identify globally distributed bulk material composition in the spectral range from 1.0 to at least 5.0 μm with a spectral resolution better than or equal to 10 nm and over a wide range of spatial scales (from 10 km/px to 100 m/px or better). | MAJIS | |||