Showing posts with label ESA. Show all posts
Showing posts with label ESA. Show all posts

Sunday, August 19, 2012

Proba-1 is Back in Business.

ESA's Proba-1 microsat was built and launched by the ESA as a proof-of-concept for semi-autonomous Earth observation - operators can upload coordinates and the satellite will autonomously image that location. The satellite ended up turning into a heavily-used science tool, but it almost shut down in May due to star tracker degradation. 


Proba-1 captured this image of London's Olympic Park
 neighborhood.   Credit: ESA 
Many small satellites use star trackers to orient themselves. The star trackers point behind the satellite (away from the Sun and Earth) and take pictures of star fields, which they can identify and use to calculate the satellite's orientation.  The CCD camera's attached to Proba-1's star trackers had sustained severe radiation (they were 5 years older than the planned lifetime for Proba-1), and the radiation had created permanent damaged or "hot" pixels which  show up in images as white spots. The star trackers were mistaking hot pixels for stars, and sending incorrect coordinates to the main satellite computer, causing it to error out or mispoint. 

Proba-1 was saved by a software patch written specifically for the satellite, which - once loaded - allowed the star trackers to distinguish between hot pixels and real stars. The star trackers are apparently working "as good as new" now, even with degraded CCDs. The proof is in the pudding - at the right is a farewell shot of Olympic Park that the satellite shot last week.

Saturday, May 26, 2012

Can Constellation Rise from the Ashes?

Back in 2010 the Obama administration canceled Constellation, Bush's space program that would have sent US astronauts back to the moon, and eventually to Mars and beyond. I do not agree with President Bush on very much, but his ambition and vision for NASA was laudable, and I was sad when they cancelled Constellation. Despite being “over budget, behind schedule, and lacking in innovation due to a failure to invest in critical new technologies” according to the White House's budget plan, Constellation did provide an exciting and inspiring goal: Mars. The same cannot be said of Obama's replacement plan to focus on "building block technologies" and eventually send US astronauts to an asteroid. The goal is not nearly as romantic, and half the US population thinks it has already been accomplished. Moreover, with the recent explosion of Planetary Resources onto the public stage, we now see that there are market forces sufficient to propel private sector missions to asteroids; the same cannot be said of missions to Mars. In this new age of privatized space, NASA's main goal should be to fund innovative research and missions that would not otherwise be funded due to a lack of immediate profitability. But I digress. 


The Liberty launch vehicle combines the proven systems from NASA's space shuttle fleet and 
Europe's Ariane 5 expendable rocket. This graphic shows how they combine into the new 
ATK-Astrium Liberty rocket. CREDIT: ATK
It now seems that Constellation might just make like a Phoenix and rise from the congressional ashes. Development of the Orion Crew Module, which would have carried astronauts to Mars, has continued under the new title of "Multi-Purpose Crew Vehicle" (MPCV) since program cancellation. And now it looks like the heavy-lift vehicle, (née Ares 1), which would have propelled Orion into space, is not completely dead either. On May 9th, Alliant Techystems (better known as ATK) announced plans to combine the first stage of the Ares 1, a five-stage solid rocket booster, with the second stage of the European Space Agency's Ariane V rocket, which has been in use since '96, to make the "Liberty Rocket". These rocket stages would be topped with ATK's own Orion spinoff, with a composite structure and less robust heat shield than the metal Orion system since ATK's version would only be reentering the atmosphere from LEO instead of deep space and thus have half the energy to dissipate upon reentry. ATK plans to develop the Liberty Rocket system into a full-fledged commercial enterprise, carrying crew and cargo into low earth orbit for both NASA and other commercial space venture companies. ATK thinks it can move quickly through development and testing since the first two rocket stages have already been tested thoroughly. They hope to launch their first test flight by 2015.


I'm glad to see that the billions of dollars and thousands of hours of hard work already poured into Orion and Ares may not have been for naught, but I have reservations about the frankenstein nature of Liberty. Rand Simberg, in a great summary of the program, pointed out that using the Ariane V as a second stage (rather than as a first stage, as it has been used by the ESA) will mean coordinating in-flight ignition of the very complex combustion engine. The difficulty of pulling this off is one of the reasons that the Space Shuttle's SSME was abandoned by NASA's Constellation team for the J2-X. 



I also can't imagine that integrating 3 different rocket stages, built by three different companies, will yield an elegant, cost-effective, or scalable result. The Ariane 5 brings 15 years of ESA heritage technology with it, the Ares rocket undoubtedly possesses the marks of 60+ years of NASA history, and the Orion capsule is being developed by Lockheed Martin, which has its own hefty share of heritage. The plan greatly undervalues the benefits of in-house design. SpaceX, for example, built their entire system (rocket and capsule) from scratch in-house. The mechanical engineers building the Falcon engines eat lunch with the electrical engineers designing the Dragon capsule and the systems engineers building the operational plans (I saw this with my own eyes when I visited SpaceX headquarters in 2010). While an ATK systems engineer will have three sets of clumsy and likely incomplete documentation to sift through, and none of the original designers to help with the task, a SpaceX engineer who wants to know why something was built a certain way merely has to find the person who designed it and ask. ATK's kludged-together rocket might be cheap and fast now, but I doubt that it will be scalable or easily updated in the long-term. 


In any case, it is likely that Liberty - which will require support from the Ares team - will receive support from members of Congress who championed Constellation and would like to see those jobs return to their districts. It will be interesting to see how Liberty changes course once it enters the political sphere.

Saturday, May 12, 2012

Envisat Redlines

Yesterday operators called off the resuscitation effort on Envisat, the European Space Agency's massive Earth-imaging satellite, after a month of unresponsiveness from the 10 year old satellite. There are several possible causes of the loss of communication. According to space.com, "The failure of a power regulator may be blocking the satellite's telemetry and telecommand systems, ESA officials said. There may have also been a short circuit on board that plunged Envisat into a protective "safe mode," then a second malfunction that left the satellite in an unknown state, incapable of receiving commands from Earth. As a fellow operator, my heart goes out to the Envisat Ops team. I can't imagine anything more frustrating than troubleshooting an unknown anomaly in the blind, with the whole space world watching. 

Despite having no comms, the ESA was able to verify that the solar arrays were still deployed thanks to a neat photo from the CNES Earth-observing Pleiades satellite:
Envisat, as images by Pleiades. Source: CNES 
The ESA says that operators will continue to command in the blind and consider failure scenarios for the next couple months. (I imagine they will also be job hunting!) Assuming they cannot raise Envisat from the dead, the satellite will be the latest casualty in the shrinking fleet of Earth-observation satellites. 
Source: Nature.com
Looks like there's going to be a vacuum in the industry pretty soon. Hmmmmm. Maybe an innovative startup could find a way to take advantage?



Though Envisat's death is sad, we should remember that it had a meaningful and long life, (it's initial lifetime projection was only 5 years) and it died doing what it loved.