Juno spacecraft set to start work in a screamingly fast orbit around Jupiter
For five years, the Juno spacecraft has been flying at a record setting 165,000 miles-per-hour, faster than any other man-made object in history. In the next 24 hours, it will fire its thrusters for 35 minutes to slow down to a mere 130,000 miles per hour so that it can careen into a perilously low orbit around our solar system’s largest planet, Jupiter. At first, communication with the spacecraft will be extremely limited, but over the next two years, we will be getting an amazing set of data on Jupiter, complete with new panoramic images of territory we’ve never been able to see clearly before.
While Jupiter is obviously a larger and closer target than Pluto or Comet 67P, getting a spacecraft in orbit to collect data hasn’t been a simple task. Rather than fly straight to Jupiter, Juno actually flew out past Mars before returning to Earth in order to use our planet’s gravity like a big sling-shot. This allowed for the spacecraft to reach it’s break-neck speeds (which would turn a three-day flight to the moon into a two-hour trip). Upon reaching Jupiter, Juno will be setting another record as the longest flight for a solar-powered craft, which of course complicates what kind of maneuvering it will be capable of. In order to maximize exposure to the sun, the satellite will orbit over and under Jupiter’s poles, rather than its equator, so that it’s never in the planet’s shadow and can stay charged. This is critical, since the sunlight that reaches Jupiter is 23 times fainter than what we get on Earth.
Surviving a rough welcome
Once in orbit, Juno will also have to cope with an unusually high amount of radiation and charged particles that surrounds Jupiter. Juno is slated to make very long, but relatively low-altitude orbits, which means that the only way to guard sensitive electronic components from being irradiated to death is to house them in a 800-pound metal hull. The spacecraft should survive until at least February 2018, but in that time it will be taking enormous amounts of damage from the tiny but high-energy debris around Jupiter. There’s extra concern about this kind of exposure when Juno enters its first orbit, requiring that the spacecraft face away from Earth which means it will barely be able to confirm its safe arrival. To know if everything is working, two stations in NASA’s Deep Space Network will have to be searching the sky for a signal weaker than what New Horizons was able to send from as far away as Pluto. We won’t be receiving regular data from onboard instruments until November, once Juno has had a chance to settle into a safer route around its target.
Gathering data on a gas giant
Aside from demonstrating various feats of engineering, Juno is set to provide us with more information than ever before on Jupiter. We know that the gas giant is massive, with extremely dense and swiftly moving clouds that have more or less thwarted previous attempts to learn about the planet’s possible core. For instance, assuming Jupiter has a non-gas core to speak of, the atmospheric pressure at the surface would be the equivalent of having a 1000 elephants resting on your head. While the Galileo orbiter launched a probe directly into Jupiter’s atmosphere, it wasn’t really a successful survey of the planet’s composition. Instead, Juno will make over 50 orbits around Jupiter, measuring how deeply microwave radiation can penetrate the swirling clouds below. This should help measure, among other things, the water content of the planet, which can help us build a model about Jupiter’s current structure as well as it’s origins. The spacecraft will also make sure to get some unbeatable snapshots of the fifth planet while it’s at it.
Once these measurements have been made, Juno’s mission is unlikely to be extended. Juno was not sterilized before leaving Earth, which isn’t a big concern for flying around Jupiter, but could be a problem if the spacecraft’s orbit deteriorated and allowed it to crash into the moon Europa. Europa is on the short list for places where life may exist in our solar system, and if Juno is carrying any kind of microbe, we don’t want to inadvertently contaminate an ecosystem we’re not even sure exists. With this in mind, Juno will end its mission by slowing down from its record-setting speeds, at which point Jupiter’s gravity will finally be able to pull it out of orbit in a controlled crash. It seems that one of the hard parts of learning more about space is that even the best toys can’t last forever.
Source: Juno is closing in on Jupiter by Christopher Crockett, Science News