Table 5.
Callisto
| Objectives | Investigations | Measurement Requirements | Instruments | |
|---|---|---|---|---|
| CA. Characterise the outer shells, including the ocean. | CA.1 | Explore the structure and properties of Callisto’s icy crust and liquid shell. | CA.1a. Measure subsurface dielectric properties and estimate density of buried scatterers in targeted regions by obtaining profiles of subsurface dielectric horizons and structures down to a few kms (maximum depth from 1 to 9 km depending on the crust properties and with vertical resolution ranging from ∼50 meters to 1% of the target depth). | RIME |
| CA.1b. In regions co-located with subsurface profiles: Acquire precise topography at 1 meter vertical resolution along-track at 100-meter (goal: a few tens of meters) horizontal resolution. | GALA | |||
| CA.1c. Measure topography on the order of 0.5 km/px spatial scale and better than or equal to 50 meter vertical resolution over regions of high interest and along subsurface profiles for generation of DTM for RIME data interpretation. | JANUS | |||
| CA.2 | Characterise the space plasma environment to determine the magnetic induction response from Callisto’s ocean. | CA.2a. Measure three-axis magnetic field components at 32 to 128 Hz with a resolution of 0.1 nT across multiple flybys at different orbital phases to determine the induction response at multiple frequencies (related to satellite orbital and Jupiter rotation time scales). | JMAG | |
| CA.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. | PEP | |||
| CA.2c. Measure electric field vectors from 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 | |||
| CB. Determine the composition of the non-ice material | CB.1 | Characterise surface organic and inorganic chemistry, including abundances and distributions of materials and volatile outgassing. | CB.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 100 m/px or better), 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 compounds known or expected to exist on the surface. Determine bulk material composition, grain size, porosity, crystallinity, and physical state of water ice in the spectral range from 1 to 4 microns with a spectral resolution better than or equal to 10 nm over a wide range of spatial scales (from 10 km/px to 100 m/px or better) and illumination conditions. Determine the composition, distribution and physical characteristics (grain-size, physical state) of volatile materials on the surface. Determine the origin and geologic evolution of non-water-ice materials, including the role of geologic processes by making observations in the wavelength range from 0.4 to at least 5 μm with a spectral resolution better than or equal to 10 nm and spatial resolution better than or equal to 1 km/px of representative features. Observations need to be co-registered with higher-resolution panchromatic images. | MAJIS |
| CB.1b. Acquire two-dimensional spectral-spatial images in the range 100 to 200 nm with a spectral resolution better than or equal to 2 nm and a spatial resolution from 5 km/px to 1 km/px or better. Determine the composition, distribution and physical characteristics (grain-size, physical state) of volatile materials on the surface, including measurements in the wavelength range of 100- to 200 nm at 2 nm spectral resolution to identify O3, H2O2 and other species. | UVS | |||
| CB.1c. Measure the volatile content (i.e. water, carbon dioxide, methane, ammonia, and noble gases) of potential outgassing sources from the near subsurface or deeper interior over a mass range better than 300 Daltons with a mass resolution better than 500. 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 | |||
| CB.1d. Image at medium-resolution (∼100’s m/px) to characterize large parts of the surface in four spectral band passes (e.g. 0.4, 0.67, 0.76, 1.0 μm) in the wavelength range of 350 nm to 1.0 μm including multiphase coverage for measurements of surface physical properties. Acquire high-resolution (better than 50 m/px) imaging of selected targets. Requires repeat pass coverage of areas of interest to assess temporal variations. Determine the origin and geologic evolution of non-water-ice materials, including the role of geologic processes by making high-resolution panchromatic images (<1 km/pxl) of representative features. | JANUS | |||
| CB.1e. Identify globally distributed bulk material composition from polarized continuum observations of the surface in the 600 GHz band under different off-nadir angles. | SWI | |||
| CB.1f. Characterize the ionized part of the volatile outgassing by measuring the electron and ion densities (10−4–105/cm3) and ion drift speed (<200 km/s) close to Callisto with good time resolution (< 10 s). This requires also measurements of electric field vectors (DC–45 MHz), magnetic field vectors (0.1–20 kHz), density perturbations (δn/n, DC–10 kHz), electron temperature (0.01-100 eV), spacecraft potential (+/−100 V), and the mass and size distribution of dust for dust >1 μm. The DC electric field measurements need an accuracy better than 1 mV/m. | RPWI | |||
| CB.2 | Relate material composition and distribution to geological and magnetospheric processes. | CB.2a. Map large parts of the surface at medium resolution (∼100’s m/px) in four spectral band passes (e.g. 0.4 μm, 0.67 μm, 0.76 μm, 1.0 μm) in the wavelength range of 350 nm to 1.0 μm. | JANUS | |
| CB.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°. 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 neutral exospheric composition with sufficient sensitivity and to sufficient mass resolution to identify major volatile species with mixing ratios better than 1%. Requires open source positive ion spectrum to characterize the composition of ionospheric plasma, open source neutral spectrum for density profiles of sputtered species, and closed source neutral spectrum. | PEP | |||
| CB.2c. Measure the surface reflectance in the wavelength range from 0.4 to at least 5 μm to identify surface composition and relate it to geologic units and weathering processes. Identify and map the distribution of products of radiolysis and ion bombardment (e.g. H2O2, O3, H2CO, H2CO3) over the wavelength range from 1.0 to 2.0 μm at better than or equal to 5 nm spectral resolution and from 2.0 to greater than or equal to 5 μm at better than or equal to 10 nm spectral resolution. | MAJIS | |||
| CB.2d. Measure the surface reflectance in the wavelength range from 0.1 to 0.2 μm to identify surface composition and relate it to geologic units and weathering processes. Identify and map the distribution of products of radiolysis and ion bombardment (e.g. H2O2, O3, H2CO, H2CO3) over the wavelength range of 100 to 200 nm with spectral resolution better than or equal to 2 nm. | UVS | |||
| CB.2e. Perform radiometric-polarized measurements in the 600 GHz band and under different off-nadir angles to constrain the thermophysical properties of the ice, regolith and ice-regolith mixtures down to a depth of a few cm. | SWI | |||
| CB.2f. 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 | |||
| CB.2g. In regions co-located with subsurface profiles: Acquire precise topography at 1 meter vertical resolution along-track at 100-meter (goal: a few tens of meters) horizontal resolution. | GALA | |||
| CB.2h. Measure subsurface dielectric properties in targeted regions by obtaining profiles of subsurface dielectric horizons and structures down to a few kms (maximum depth from 1 to 9 km depending on the crust properties and with vertical resolution ranging from ∼50 meters to 1% of the target depth). | RIME | |||
| CB.3 | Characterize the ionosphere and exosphere of Callisto. | CB.3a. Identify and determine column densities of atmospheric species across the globe at 1 km spatial resolution or better using stellar occultations. Requires coverage in the wavelength ranges of 0.4 to 2.0 μm with spectral resolution better than or equal to 5 nm and 2.0 to 5.0 μm with a spectral resolution better than or equal to 10 nm. Obtain global, two-dimensional, spectral-spatial images at better than 50 km/px spatial resolution in the wavelength range of 0.1- to 5-microns to measure CO2, C, O, CO, O+ and other species in absorption and/or emission. spectral resolution better than 10 nm for wavelengths greater than 1.0-micron. Map atmospheric emissions by scanning perpendicular to the limb from ∼300 km above the surface to the surface of the satellite (at steps of 5 km). Requires measurements in the wavelength range 1.0 to 2.0 μm at better than or equal to 5 nm from and 2.0 to 5 μm at better than or equal to 10 nm. | MAJIS | |
| CB.3b. Identify and determine column densities of atmospheric species across the globe at 1 km spatial resolution or better using stellar occultations. Requires coverage in the wavelength ranges of 100- to 200- nm at 1 nm spectral resolution. Obtain global, two-dimensional, spectral-spatial images at better than 50 km/px spatial resolution in the wavelength range of 100- to 200-nm to measure CO2, C, O, CO, O+ and other species in absorption and/or emission. Requires spectral resolution of 2 nm. Map atmospheric emissions by scanning perpendicular to the limb from ∼300 km above the surface to the surface of the satellite (at steps of 5 km). Requires measurements in the wavelength range of 100 to 200 nm at 2 nm spectral resolution. | UVS | |||
| CB.3c. Measure neutral exospheric composition with sufficient accuracy and to sufficient mass resolution to identify major volatile species with mixing ratios better than 1%. Determine positive ion spectrum of sputtered ions with M/ΔM ≥ 20. Determine the particle precipitation distribution 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 | |||
| CB.3d. 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 inhomogeneities (dn/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. | RPWI | |||
| CB.3e. Measure three-axis magnetic field components at 32 to 128 Hz with a resolution of 0.1 nT across multiple flybys at different orbital phases. | JMAG | |||
| CB.3f. Determine the distribution of water vapour in the atmosphere from water line observations in the 600 GHz band. Determine the hydrogen and oxygen isotopic ratios of water. | SWI | |||
| CB.3g. Characterize and map the ionosphere by performing radio occultations over as wide a range of longitude space as possible. | 3GM | |||
| CC. Study the past activity | CC.1 | Determine the formation and characteristics of tectonic and impact landforms. | CC.1a. Acquire precise topography at 1 m vertical resolution and better than 1 km horizontal resolution with selected targets at 100-meter (goal: a few tens of meters) horizontal resolution. In regions co-located with subsurface profiles: Acquire precise topography at 1 meter vertical resolution along-track at 100-meter horizontal resolution. | GALA |
| CC.1b. Characterize large parts of the surface at medium resolution (∼100’s m/px) in four spectral band passess (e.g. 0.4 μm, 0.67 μm, 0.76 μm, 1.0 μm) in the wavelength range of 350 nm to 1.0 μm. Requires solar illumination at mid-morning to mid-afternoon local times. Acquire high-resolution (better than 50 m/px) imaging of selected targets. Measure topography on the order of 0.5 km/px spatial scale and better than or equal to 50 meter vertical resolution over regions of high interest. | JANUS | |||
| CC.1c. Measure surface reflectance in the wavelength range from 0.4 to greater than or equal to 5 μm with 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 and spatial resolution better than or equal to 20 km/px. Requires targeted high spatial/high spectral observations of important geologic units and terrain types. | MAJIS | |||
| CC.1d. Identify and locally characterize subsurface compositional horizons and structures by obtaining profiles of subsurface dielectric horizons and structures down to a few kms (maximum depth from 1 to 9 km depending on the crust properties and with vertical resolution ranging from a minimum of ∼50 meters to 1% of the target depth) to estimate subsurface dielectric properties and the density of buried scatterers in targeted regions. | RIME | |||
| CC.2 | Investigate the interior of Callisto, with a special emphasis on its degree of differentiation. | CC.2a. Derive information on the static shape by measuring range to the surface during multiple fly-bys. | GALA | |
| CC.2b. Image the limb for shape determination by acquiring multiple images at better than 1 km/px resolution. Perform astrometric determination of the rate of change of Callisto’s orbit by acquiring multiple images of Callisto from a distance including background stars with a position accuracy of at least 1 km. Determine the mean spin pole direction (obliquity) to better than 1 km by developing a geodetic control network (∼20 points) at a resolution better than 500 m/px. | JANUS | |||
| CC.2c. Determine the static gravity field at low order by measuring the range-rate from spacecraft tracking during multiple flybys to derive the 2nd degree gravity field and local potential anomalies. Requires range-rate measurements with an accuracy ∼0.01 mm/s over 60 s integration time. If tracking is available for all the flybys, the gravity field may be stimated up to degree 3 and the Love number k2 with an accuracy of 6E-2 | 3GM | |||
| CC.2d. | ||||
| CC.3 | Constrain global and regional surface ages. | CC.3a. High spatial resolution observations (better than or equal to 1 km/px) from 0.4 to 5 μm (spectral resolution: better than or equal to 5 nm from 0.4 to 2.0 μm, better than or equal to 10 nm from 2.0 to greater than or equal to 5 μm), with emphasis on the spectral differences between geologic features (multi-ring basins, craters) and the surrounding areas. Medium spatial resolution (better than or equal to 10 km/px) on large areas to map leading/trailing asymmetries. | MAJIS | |
| CC.3b. Perform detailed morphological characterization of selected features through imaging at better than or equal 50 m/px spatial scale. Determine the distribution and morphology of impact craters by mapping in four colors (visible to near-IR) for large areas at scales ∼400 m/px and in a single color at regional scales (∼100 m/px) with near-uniform lighting conditions and solar phase angles less than or equal to 45 degrees. | JANUS | |||
| CC.3c. High spatial resolution observations (better than or equal to 1 km/px) from 0.1 to 0.2 micron (spectral resolution: ≤ 2 nm), with emphasis on the spectral differences between geologic features (multi-ring basins, craters) and the surrounding areas. Medium spatial resolution (better than or equal to 10 km/px) on large areas to map leading/trailing asymmetries. | UVS | |||
| CC.3d. Identify and locally characterize subsurface compositional horizons and structures by obtaining profiles of subsurface dielectric horizons and structures down to a few kms (maximum depth from 1 to 9 km depending on the crust properties and with vertical resolution ranging from ∼50 meters to 1% of the target depth) to estimate subsurface dielectric properties and the density of buried scatterers in targeted regions. | RIME | |||
| CC.3e. In regions co-located with subsurface profiles: Acquire precise topography at 1 meter vertical resolution along-track at 100-meter (goal: a few tens of meters) horizontal resolution. | GALA | |||