Io Volcano Observer
|Operator||Under evaluation by NASA|
|Mission type||Orbiter, fly-by|
|Launch vehicle||Atlas V (401)|
|Mission duration||18-month nominal mission at Jupiter|
|Orbital insertion date||July 2021|
|Orbits||At least 6|
|Power||280–320 W using 2 ASRGs|
Io Volcano Observer (IVO) is a proposed unmanned spacecraft that, if approved and launched, would orbit Jupiter and perform at least seven flybys of Jupiter's moon Io. IVO has been proposed to NASA by the University of Arizona as both a science and engineering mission, originally as part of NASA's Discovery & Scout Mission Capability Expansion (DSMCE) concept-study program. Currently, the mission is a possible proposal to be submitted for NASA's Discovery program. As such, IVO has not been funded and it is still in its conceptual phase; if selected, its intended launch window would be in January 2015.
IVO is a low-cost, outer-planet mission that would explore Io's active volcanism and impact on the Jupiter system as a whole by measuring its global heat flow, its induced magnetic field, the temperature of its lava, and the composition of its atmosphere, volcanic plumes, and lavas.
Active volcanism was discovered on Jupiter's moon Io by Voyager 1 in March 1979. This significant amount of volcanism on Io is the result of tidal heating, a process that has also resulted in increased internal heat within other outer planet satellites, such as Enceladus and Europa. On both of these latter moons, the tidal heating has allowed liquid water near the surface of these moons, dramatically affecting their geology and providing a possible habitat for life. Since its discovery in 1979, the volcanic activity on Io was observed by ground-based astronomers as well as the Galileo, Cassini, and New Horizons. Galileo flew by Io seven times over the course of its nearly-eight-year mission at Jupiter. However, Galileo's low downlink bandwidth resulting from its broken high-gain antenna, camera and spectrometer problems, and safing events that occurred during several of the encounters limited the amount and quality of data that could be returned from these flybys. Both Cassini and New Horizons flew by the Jupiter system at distances greater than the orbit of Callisto, the outermost of the Galilean satellites, limiting the resolution and time span of their data.
Io Volcano Observer was a concept study for NASA's Discovery & Scout Mission Capability Expansion (DSMCE). The purpose of the program was to see what types of missions could be performed under a Discovery mission cost cap ($425 million) if a government-supplied Advanced Stirling Radioisotope Generator (ASRG) was used as a power source. From the 40 proposals submitted to NASA's DSMCE Program, nine were selected for further study. This process was completed in February 2009 when the IVO team and the other groups submitted their final reports to NASA. Currently, NASA is soliciting for proposals for the next Discovery mission, of which IVO will likely be one such proposal.
IVO's launch would be with an Atlas V (401) rocket during a launch window in January 2015. Following launch, the spacecraft would perform a VEEGA trajectory, using a gravity assist at Venus in January 2016 and two at Earth in February 2017 and February 2019 to send the spacecraft on a Jupiter-bound trajectory. Following an Io flyby on its way in, the Io Volcano Observer in July 2021 would execute a Jupiter Orbital Insertion burn to go into an inclined orbit around Jupiter. Following an initial six-month orbit, IVO would encounter at 6-10 times during an 18-month primary mission. As IVO would be an inclined orbit (~49°), during each of these encounters would approach Io from over its south polar region, make its closest approach near the equator of Io at distances ranging from 100 to 1000 kilometers, and depart Io over its north polar region. To aid in change detection, the spacecraft would also encounter Io near the same point in Io's orbit, keeping similar lighting conditions over the course of the nominal mission. Following the primary mission, if the spacecraft and power source remains healthy, an extended mission could be approved. This extended mission could include pumping up the orbital period of IVO to one year in length as part of a test of the ASRGs life span, to monitor Io for changes over a longer time span, and to possibly encounter one of Jupiter's outer irregular satellites. Such an extended mission could last up to eight years, with the potential for up to eight additional encounters.
The science objectives of this proposed mission are:
- Understand Io’s currently active volcanism and implications for volcanic processes on other planetary bodies throughout geologic time.
- Understand Io’s interior structure and tidal heating mechanisms and implications for the coupled orbital-thermal evolution of satellites and extrasolar planets.
- Understand the processes that form mountains and paterae on Io and the implications for tectonics under high-heat-flow conditions that may have existed early in the history of other planetary bodies.
- Understand how Io affects the Jovian system, and implications for the study of otherplanetary systems.
- Seek evidence for activity in Io's deep interior and understand the generation of internal magnetic fields.
The high-data rate during Io flybys by IVO rules out the use of solar panels like the ones that have kept the Mars orbiters functioning for years. If selected by NASA, the Io Volcano Observer would be the test flight of two of the new Advanced Stirling Radioisotope Generator (ASRG), which is a prototype meant to provide availability of long-lived power supplies for planetary missions. The ASRG is a radioisotope power system using Stirling power conversion technology and is expected to generate 140–160 W of electrical power; that is four times more efficient than RTGs currently in use. Its mass is 20 kg and will have a nominal lifetime of 14 years.
- ≥14 year lifetime
- Nominal power : 140 W
- Mass ~ 20 kg
- System efficiency: ~ 30%
- 2 GPHS 238Pu modules
- Uses 0.8 kg plutonium-238
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- James L., Green (June 23, 2008). "Planetary Science Division Update" (PDF). NASA. Retrieved 10 November 2009.
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- Perry, J.; et al. (2007). "A Summary of the Galileo mission and its observations of Io". In Lopes, R. M. C.; and Spencer, J. R. Io after Galileo. Springer-Praxis. pp. 35–59. ISBN 3-540-34681-3.
- McEwen, Alfred (December 12, 2008). "Io Volcano Observer (IVO)" (pdf). Berkley Io Workshop. Retrieved 2010-02-08.
- McEwen, A.; et al. (2010). "Science Rationale for an Io Volcano Observer (IVO) Mission" (PDF). LPSC XLI. Abstract #1433.