|
|
|
Comet impact: a smashing thought
LIKE ethereal fleeting objects of light, comets stream across the skies with icy tails behind them leaving mystery and beauty behind. What actually lies within these celestial bodies is still not very clear. Today, astronomers do not know much about the composition of a comet aside from the fact that they consist of some amount of rock, ice and gas.
In the summer of 2000, comet 1999 S4 LINEAR disintegrated within view of many Earth-based telescopes, giving a chance to the astronomers and scientists to study the interior of the comet.
It was discovered that comet, LINEAR contained much less water than previously thought. But since this was the only example, scientists had no way of knowing whether the comet was of a regular composition or a special case.
To get a clearer idea and picture, comets will have to be studied in greater detail. A challenge that Nasa and the European Space Agency are trying to overcome.
The most challenging part of studying a comet from space is that mission planners have very little idea about their intended target, making it difficult for the spacecraft to be programmed to look for one.
This poses a problem of how the targeted comet can be found and how successfully it can be imaged. Within the comet’s interior lie the secrets to the formation of the solar system as they carry the rocks and ice remnants of the universe in the beginning.
The idea
On the charts is Nasa’s upcoming Deep Space Mission to understand what lies beneath the serene interior of Comet 9P/Temple 1. At Ball Aerospace and Technologies, two interesting spacecraft are being designed. One is the “flyby” spacecraft, which will take images from a front row position once it reaches the comet and the other is the “impactor.”
This spacecraft will do exactly as it says on its nametag. It will crash into the comet, impacting it at full speed. Both the spacecraft are being tested for launch next year in December.
The two part hit and run mission will commence with the launch in December 2004 for a 6-month route to the comet Temple 1.
The two spacecraft, which will be combined, will image the comet on its approach. The flyby spacecraft will point it’s high precision telescopes at the comet 24 hours before the impact and then release the “impactor” in the path of the comet.
The “impactor is an autonomous spacecraft in its own right and will plunge into the sunlit side of the comet to crash into the surface. The impact will leave a crater anywhere from the size of a house to a football field.
All this will be closely watched by the “flyby” spacecraft which will be at a safe distance, (approximately 300 miles or 500 kilometres), but still be able to get a clear picture of the impact and the debris and surface material that flies out when the comet’s interior is struck.
Images from both, the “flyby” and the “impactor” will be sent back to Earth in real -time. Nasa is basing this on a somewhat patriotic note by planning the impact on the 4th of July, 2005. Making it a celestial show of fireworks for Independence Day in the United States.
Monte Henderson, Deputy Program Manager on the Deep Impact project at Ball Aerospace stated, “there’s a lot of newness in this program. This is our company’s first program that sends us into deep space”.
In a spick’n’span room, engineers and technicians dressed in white smocks are busy with the rechecking of all components of the spacecraft and the “Mini-Me” impactor.
He further stated to SPACE.com, “in a sense, this program is building two 100-percent capable spacecraft. And it has been a big challenge”.
About the impactor, which gets treated as the “little brother” to the “flyby” and also shares a few components like electrical components and control units with its bigger counterpart, Henderson says, “the impactor has become a very smart, fully-autonomous spacecraft. It’s capable of maneuvering and taking care of its own positioning and targeting completely independent of what’s going on with the flyby spacecraft”. The impacter packs 220 pounds of pure copper.
Secrets that lie beneath
While engineers, scientists and technicians fervently work on the two-part spacecraft, very little is known about their intended target.
Discovered in 1867, there is not much that is known about Temple 1. It has made many passes through the inner solar system every 5.5 years, making it a good study for evolutionary change.
It was previously thought that its size was 5 kilometres in diameter but recent findings say that it is smaller.
Will it be solid or just a collection of debris under the icy shell? In which case the Impactor will just shoot through the comet. As Henderson rightly said, “it’s an evolving science of what this comet is…and what it’s made of”.
The Jet Propulsion Laboratory in Pasadena California will manage the flightpath to the comet, the world’s leading experts in deep space missions and are also managers of Deep Impact.
Lucy McFadden, a science team member for Deep Impact from the University of Maryland (USA) said that observations of the comet are already underway. “In a year, we’ll have small telescope observers measuring the comet’s magnitude.
The advantage of observation through a small telescope is that there is potential to observe the comet more frequently and to get good temporal coverage of its brightness variation as it comes back into the inner solar system,” she noted.
The whole team consists of 250 scientists, engineers, educators and managers. They are researching what the spacecraft will encounter on their approach to the comet.
“Its rotation rate is known pretty well. It is rotating slowly, so we won’t hit and then lose sight of the crater due to rotation,” stated McFadden. More mystery and questions still prevail.
Will the sunlit side have too many cavities as to limit the opportunities of the impact? They are counting on it being similar to Comet Borelly which Nasa’s Deep Space 1 spacecraft flew by in September 2001.
The comet had a sufficiently sunlit exposed surface. McFadden explained, “after that the biggest uncertainty is in the nature and structure of the comet itself, and that is why we are doing the experiment. How big a crater we will excavate and how deep will the crater be?”
She further stated, “We need the observational science community to make complementary observations, both prior to encounter — to characterize the comet and enable us to plan the experiment — as well as follow the event from Earth.”
Will the experiment and mission be helpful in diverting any threat to Earth? In a response to questions via email, A’Hearn of the University of Maryland said, “Yes, it will provide important information on the physical properties that will be essential to planning any threat diversion. However, it will be applicable only to the small subset of potential impactors that are comets (or extinct comets).”
Termed “a good learning experiment” by Monte Henderson, the Deep Impact Mission is what researchers are looking forward to. “We’re less than a year from ship. This is when it gets really exciting. Everybody has been building individual pieces. Now we put it all together and say: ‘Prove that it works,’” says Henderson.
If all goes according to plan, and the Deep Impact Mission is successful as everyone hopes, we will have an insight into what these fleeting, shiny objects are all about.
The writer
|
|
|
|
