Update (05.28.14): According to the team at the OCC, Chandra was unharmed during this new meteor shower. They report that passage through the stream was 'thankfully unremarkable.' According to all of their information, there was no evidence for any type of impact and it was 'smooth sailing.'
This week, sky watchers will be treated to a special event: a new meteor shower. Meteor showers occur when Earth, on its orbit around the Sun, passes through the debris left behind by a comet. There are some debris fields that Earth passes through every year and produce regular meteor showers that many people have heard of. These include the Leonids in November and the Perseids in July and August.
The meteor shower that will occur on May 23rd and 24th will be caused by the wake of Comet 209P/Linear and has been dubbed the Camelopardalids. (Meteor showers are named after the constellation that they appear to be coming from, which in this case is Cameloparadis, the giraffe.) Comet 209P/Linear was discovered in 2004, and it travels in an orbit that only crosses with Earth's once every five years as it loops around the Sun. This means that Earth only rarely crosses paths with the trail of material left behind it. Comet experts, however, calculate that this week Earth is due for an encounter with a clump of 209P/Linear's wake, perhaps for the first time ever.
Some researchers have predicted this will be a very active meteor shower that could produce up to 200 meteors an hour. While this could be an exciting early morning show for sky watchers who can get outside, a team at the Chandra X-ray Center's Operation Control Center (OCC) will be busy preparing for and dealing with the event inside.
Even though much of the debris in meteor showers is very tiny, it can pose serious potential risks for spacecraft like Chandra. There are two main concerns: the first is that particles moving at very high speeds will generate electric fields that could disrupt the electronics aboard the spacecraft. The second big worry is that a particle would impact Chandra, causing damage to a key instrument or other important piece of the telescope.
While the team at the OCC has handled many meteor showers in Chandra's nearly 15 years of operations, the Camelopardalids are different because there is relatively little known about the stream of material that Earth (and Chandra) will pass through. Because of this uncertainty, the Mission Planning Team is taking extra precautions.
In fact, it's the Mission Planners to think of everything that could possibly go wrong – and then have plans in place to prevent those things from happening. This includes having contingencies in place in case something unusual happens in the two days before the meteor shower even starts, just to make sure they can safeguard Chandra.
Several hours before the meteor shower is expected to begin, the team will make sure that the spacecraft is pointed in the opposite direction of where the meteors are coming from (that is known as the "radiant" of the meteor shower.) They will also feather, or turn, Chandra's solar arrays in a direction to minimize the amount of their surface area that will be exposed to the oncoming meteors.
In 2011, the team at the OCC shifted its approach to meteor showers during the Draconids. They realized that only the very high-speed particles posed a threat to the electronics onboard. Rather than "safing" all of the instruments, they calculated they could continue have the telescope perform science observations as long as it was pointed away from the radiant.
The Camelopardalids are expected to have even slower moving particles than the Draconids, so the plan would have been to continue observations of the sky. Like most space-based telescopes, observing time on Chandra is very valuable so the team at the OCC is always looking to maximize it. Unfortunately, the peak of the meteor shower will begin when Chandra is traveling through the Earth’s radiation belts, as it does during one of its orbits that take it a third of the way to the Moon.
To protect the spacecraft during these regular trips through the potentially damaging radiation, Chandra does not perform science observations of the sky. Instead, the team uses this "down time" to conduct calibration observations of the instruments that can be done safely within the spacecraft. (Calibration observations are used to assess the state and performance of the instruments on board.)
Even though Chandra will exit the radiation belts several hours before the meteor shower is over and could theoretically begin science observations, the team decided against it. That's because the solar arrays would have to be moved, and the risk outweighed the potential reward of that observing time. The result is that one of Chandra’s instruments – known as the Advanced CCD Imaging Spectrometer, or ACIS -- will get a much longer calibration observation than usual. (That extra calibration time will be put to good use as scientists never complain about having too much data for anything.)
These are just some of the many details and plans that are being put into place by staff at the OCC to protect Chandra during this meteor shower. Comet forecasters think the peak of the Camelopardalids will be between 2:00 and 4:00am Eastern time. If there are clear skies in your area, try to get outside to take a look if you are awake. If you do, remember that there are many people hard at work trying to ensure the safety of our greatest telescopes in space.
-Megan Watzke, CXC