Decommissioned WISE Gets a New Mission – Asteroid Hunter
NASA Spacecraft Reactivated to Hunt for Asteroids, NASA
“A NASA spacecraft that discovered and characterized tens of thousands of asteroids throughout the solar system before being placed in hibernation will return to service for three more years starting in September, assisting the agency in its effort to identify the population of potentially hazardous near-Earth objects, as well as those suitable for asteroid exploration missions.
The Wide-field Infrared Survey Explorer (WISE) will be revived next month with the goal of discovering and characterizing near-Earth objects (NEOs), space rocks that can be found orbiting within 45 million kilometers (28 million miles) from Earth’s path around the sun. NASA anticipates WISE will use its 16-inch (40-centimeter) telescope and infrared cameras to discover about 150 previously unknown NEOs and characterize the size, albedo and thermal properties of about 2,000 others — including some of which could be candidates for the agency’s recently announced asteroid initiative.”
Can we make more WISE telescopes?
I would limit redesign to about 20% of the components to handle obsolescence.
Cheaper to build them from scratch since they were only designed to be built once – and that was many years ago. You raise a good point though: if something works then reuse it – and require that contractors keep that in mind.
Keith, contractors already do this. Its in their best financial interest. However, it is not as straightforward as one might imagine. Obsolescence, LV changes, orbital parameter changes, mission life, and any other type of change can, and does, drive design changes on the new S/C. Even small changes can screw up the thermal, dynamics, mass and other solutions that worked on the previous S/C. Even if you want to build an identical S/C to be launched on the same LV to the same orbit, the aforementioned parts obsolescence makes it impossible if any length of time has passed.
Hence my first sentence.
I’d like to see everybody in every aspect of design, manufacture and use habitually thinking in terms of resuse all of the time. Key to this is modular component design and standardized electrical, mechanical, pneumatic, hydraulic, etc. interfaces between components and between systems. Designing and building space hardware and software will never be as simple, quick and easy as working in Legoland, but I believe we can get a lot closer to it and benefit greatly. Approaching this goal internationally will multiply its benefits many times over, so program RFPs should incentivize bidders to comply.
Other major keys to realizing reusability are increased reliability and maintainability. One area in which I think spacecraft systems are much less than they could be is in how redundancy is achieved, especially in consideration of our imminent move to BEO activities. To date, space systems have pretty much mirrored aircraft thinking in that redundancy is achieved by installing two or more identical, or nearly identical, systems. If the primary systems fails, you fall back on an identical secondary system. In some cases, like flight controls, you need two sources, or two out of three sources, to agree before you can commit to an action. The problem is that if your primary system fails for environmental or ambient condition reasons, your backups are likely to fail as well. In the more mission critical realm of space operations, redundant systems need to be of varying types, with differing strengths and weaknesses, so that if one systems fails, a non-identical replacement takes over. Once again, I’d offer incentives for compliance and perhaps even penalties for non-compliance.
Even though thinking in terms of developing reliable reusable systems will require changed design and manufacturing processes and increased costs, it is an investment that will pay off handsomely down the road, and should not present any insurmountable engineering problems if proper top-down design (and bottom-up testing) philosophies are applied. An additional “new cost” derives from the acceptance that contracts should not be awarded strictly on the basis of lowest bid — other criteria, pertaining to reusability, reliability, and life cycle costs need to become major determining factors.
They might be trying to reduce weight in every aspect of design instead, and that drives all the custom parts. Just throwing that out there, I don’t know much about that stuff. Weight is a big deal in wilderness backpacking too and sometimes you do pay more to get lighter 🙂
“sometimes you do pay more to get lighter“
As opposed to rock stars, who pay more to get heavier, and junkies, who pay more to get higher.
Mike,
I suspect you’re absolutely right, but I’d still like to see them thinking in terms of solving these challenges concurrently rather than choosing one over the other. It’s like the old Fram oil filter commercial — you can pay me now or you can pay me later — with the inescapable catch that it’ll cost more to pay later.
Turning on WISE again is a good thing for studying albedo distributions of asteroids, but completely insignificant with respect to finding asteroids that threaten Earth. That is because WISE will discover only about 50 Near Earth Asteroids per year. We need to find at least 100K Near Earth Asteroids per year in order to make an appreciable dent in the 1 million Near Earth Asteroids that threaten Earth (large enough to destroy a city).
There was another NEO related objective buried farther down in the press release:
“it will help us refine our concepts and mission operation plans for future, space-based near-Earth object cataloging missions”
“We need to find at least 100K Near Earth Asteroids per year in order to make an appreciable dent in the 1 million Near Earth Asteroids that threaten Earth (large enough to destroy a city).”
I have no idea where that one million figure comes from. The best current estimate is that there are roughly 4700 (+/-1500) Potentially Hazardous Asteroids (PHAs) with diameters larger
than 100 meters. So far, an estimated 20 to 30 percent
of these objects have been found.
http://www.nasa.gov/mission…
http://www.sen.com/news/nas…
Geoff Landis completely misunderstands the numbers he quotes. The list of PHAs he is looking at refers only to KNOWN objects. The hazard is from impacts with unknown objects. Ed Lu is correct; there are approximately one million NEAs large enough to destroy a city (e.g., a few megatons, like Tunguska). So far we have discovered ten thousand, and we are adding about a thousand a year with existing search systems. If we really want to make a dent in finding the next impactor before it finds us, we need orders of magnitude improvement in discovery rate. NEOWISE is a fine instrument for doing asteroid science, but it won’t find that many new NEAs.
Potentially Hazardous Asteroids are a subset of Near Earth Asteroids that are considerably larger than those which could only destroy a major city and whose orbits come within .05AU of Earth. Only once we find and track an asteroid can we determine if it fits into the subcategory of PHAs, so in practice we must find Near Earth Asteroids. If we want to protect ourselves from these smaller “city killers”, then we do indeed need to find and track roughly a million Near Earth Asteroids.