Jupiter Ganymede Orbiter (JGO) Concept

JGO is the ESA element of the EJSM. JGO will be built to accommodate the moderate radiation environment outside of Europa orbit. It would consist of a solar powered orbiter with 10 science instruments designed for remote sensing of Jupiter and the inner satellites and for extensive mapping of Ganymede. Prior to Ganymede arrival, JGO will intensely investigate Callisto from a resonant orbit, and make extensive observations of the Jupiter system to complement those of JEO. Additional information can be found in the EJSM Joint Summary Report..

Science Overview

Within the context of the EJSM themes and objectives, JGO will focus on its three science sub-goals: How did the Jupiter system form?; How does the Jupiter system work?; and Does the Jupiter system harbor a habitable world? The NASA-ESA Joint Jupiter Science Definition Team (JJSDT) developed the science objectives, measurements, model payload, and science value assessments for the JGO element of the EJSM. The model payload was used to assess the feasibility of the science objectives and allow for system cost estimates.

Science Objectives

1. Ganymede: Characterize Ganymede as a planetary object including its potential habitability.
2. Satellite System: Study the Jovian satellite system.
3. Jupiter: Study the Jovian atmosphere. 
4. Magnetosphere: Study the Jovian magnetodisk / magnetosphere
5. Jupiter System: Study the interactions occurring in the Jovian system.

Mission Overview

JGO launches in March 2020 on an Ariane 5 and, using a ballistic trajectory with Venus-Earth-Earth gravity assists (VEEGA), arrives at Jupiter in February 2026. Jupiter Orbit Insertion (JOI) begins a 11 month Jupiter science phase followed by a 13 month Callisto science phase and Ganymede Orbit Insertion (GOI) in May 2028. At Ganymede, both elliptical and circular orbit science phases will last about 9 months. The orbiter will ultimately impact the surface of Ganymede after running out of orbit maintenance fuel. Highlights of the science phases include:

• JOI into 13 x 245 RJ (Jupiter radii) elliptical orbit
• Sequence of swing-bys at Ganymede and Callisto Callisto Science Phase (383 days): 19 Callisto flybys at altitude of 200 km using 1:1 and 2:3 resonant orbits, allowing for (quasi) global surface coverage
• Ganymede Orbit Insertion (GOI) into 200 x 6000 km elliptical orbit
• Ganymede elliptical orbit science phase (up to 80 days)
• Maneuver to reach a low altitude (200 km), circular, quasi-polar orbit
• Ganymede circular orbit science phase up to 180 days
• End of nominal mission after about 8.9 years in February 2029

Sample JEO-JGO Timeline

Flight System Overview

The JGO flight system is comparable in size and complexity to other spacecraft for similar missions such as Rosetta or Mars Express. The concept would feature full redundancy for engineering functions, 3-axis stabilized pointing, solar power with batteries for peak power management, bi-propellant chemical propulsion, a large high gain antenna (HGA), and X-band transponders for tracking, telemetry and Ka-band precision Doppler measurements. Radiation shielding will be used to reduce radiation levels for electronic components and assemblies.

System Mass

• Launch Mass Capability, 4362 kg
• Launch Vehicle Adapter, 190 kg
• Flight System Mass (CBE), 957 kg
• Propellant (for 3000 m/s), 2562 kg
• Remaining usable launch mass, 653 kg
  (for contingency and system margin)

Subsystems	Model Payload (73 kg)
Telecom 2.8m HGA X-band (Ka band is for science only) Attitude control 3-axis stabilized with thrusters and reaction wheels Power 51 m2 LILT Solar Arrays Lithium Ion battery for peak and eclipse power management Propulsion Bi-propellant Single main engine	Micro Laser Altimeter Radio Science Package Radar Sounder VNIR Imaging Spectrometer UV Imaging Spectrometer Thermal IR Mapper Wide Angle and Medium Resolution Camera Magnetometer Plasma Package Sub-mm Wave Sounder