Saturday, June 30, 2012

The B612 Foundation

Antoine de Saint-Exupéry's Little prince on the original B612 asteroid.
On June 28th, the B612 foundation announced its plans to build, launch, and operate a deep-space telescope, Sentinel, which will find and map asteroids that could pose a danger to planet Earth. The official press release summarizes the mission:
“The orbits of the inner solar system where Earth lies are populated with a half million asteroids larger than the one that struck Tunguska (June 30, 1908), and yet we’ve identified and mapped only about one percent of these asteroids to date, said Ed Lu, Space Shuttle, Soyuz, and Space Station Astronaut, now Chairman and CEO of the B612 Foundation. “During its 5.5-year mission survey time, Sentinel will discover and track half a million Near Earth Asteroids, creating a dynamic map that will provide the blueprint for future exploration of our Solar System, while protecting the future of humanity on Earth.”
The B612 foundation has actually been around since 2001, working towards its mission of protecting Earth from a potentially disastrous asteroid impact. Prior to yesterday's announcement they had been focusing on technologies that could deflect threatening asteroids away from Earth's orbit, such as gravity tractors, kinetic impactors, and nuclear vaporization. However, they eventually realized that these technologies would be useless if no one knows the asteroid is coming, and that nobody was doing anything to find and track the most threatening asteroids. the organization's website explains: 
"NASA’s Spaceguard survey has succeeded in mapping 90 percent of the largest NEAs (larger than 1 km), yet due to the limitations of searching for asteroids using mostly ground based optical telescopes, only about one percent of these asteroids larger than Tunguska have been discovered and tracked to date. We are essentially flying around the Solar System with our eyes closed." 
The foundation estimates that in 5.5 years, Sentinel will have identified around half a million Near Earth Asteroids, with enough temporal information to project their orbits 100 years into the future. They think there is a 50% chance that the mission will identify at least one asteroid on a collision course with Earth that will need to be deflected in order to prevent a potentially catastrophic Earth impact.
The Sentinel Telescope (preliminary design by Ball Aerospace).
Source: B612

The Sentinel telescope will operate in the infrared, where asteroids stand out against the cold blackness of space, and be built by Ball Aerospace, the same folks that built the Kepler, Spitzer, and Hubble telescopes. It will be placed into an orbit similar to Venus's. This orbit will allow it to scan the side of the Sun opposite from Earth, which it would not be able to do if it were in orbit around Earth. However, it will also make operations and communications tricky because its distance from Earth will vary between 30 - 170 million miles, as opposed to the much more cozy 350 milles between Earth and Hubble. This is difficult but by no means unheard of - we have been operating spacecraft on Mars and beyond for tens of years. Current estimates put launch in 2017-2018, aboard one of SpaceX's Falcon 9 rockets.

Sentinel's orbit, which will allow it to map the side of the Sun opposite from Earth.
Source: B612 foundation. 
The B612 Foundation has signed a Space Act Agreement with NASA in June 2012, under which NASA will provide communications, tracking, and technical support for the Sentinel Mission. However, B612 is a nonprofit 501(c) 3 organization that "intends to raise the money for the Sentinel Mission in a manner similar to philanthropic capital campaigns for civic projects." If they do it right, and take advantage of flashy publicity videos and social media, I bet they could raise the necessary money very quickly - this is a subject that people can easily get excited about. 

Kudos to the B612 foundation for taking on a huge but necessary project. As John Stuart recently put it, "Do you know how rarely the news in 2012 looks and sounds how you thought news would look and sound in 2012?"

Wednesday, June 20, 2012

Intelsat IS-19 Deploys Damaged Solar Array

Intelsat's IS-19 communication satellite, which will provide telecommunications services and broadband coverage in the Pacific Ocean region, finally deployed its south solar array yesterday, after keeping it stowed for 13 days. The solar array sustained severe damage during launch, and was stuck in the stowed position for several days. Once deployed, operators estimated that the damage reduced the array's power-collecting capacity by half. The spacecraft is still operational, but will only be able to reach 75% power capacity.
Credit: Space Systems/Loral

IS-19 was built by Space Systems/Loral, in Palo Alto, CA, and launched by the Swiss company Sea Launch. Both sides continue to deflect blame for the damage, but Sea Launch did report an "unexplained pressure event" 72 seconds into the launch, which mirrors a similar event detected in the Sea Launch rocket in 2004, when launching another Space Systems/Loral satellite (Telstar 14/Estrela do Sul 1) whose solar array never deployed.

Sea Launch has released launch telemetry indicating that "all systems performed nominally throughout the launch profile...Boeing engineers did notice an unexpected, isolated event around 72 seconds after launch" . They cheekily point the finger by adding "while it is premature to speculate on its origin…it bears a striking resemblance to a prior Space Systems/Loral mission". 

It is worth noting that Space Systems/Loral has a small history of challenged solar arrays. The company also built Telstar 14R (Estrela so Sul 2), which experienced a problem deploying the solar arrays after launch as well, but was launched on a Russian Proton rocket.

The Sea Launch platform - a converted
oil rig. Credit: Sea Launch
Sea Launch is an interesting company - it launches its Zenith 3SL rockets from a converted oil rig which is towed from Long Beach, California to the middle of the Pacific Ocean right on the equator, an optimal location for launching satellites to geosynchronous transfer orbits. The company was formed in 1999 as a joint venture between companies from Norway, Russia, the Ukraine, and the United States, and is managed by Boeing. It recently emerged from bankruptcy in 2010 and has had two successful launches in as many years.

Saturday, June 16, 2012

China Sends 3 Taikonauts to Space

The Long March II-F rocket being transported to the launch pad. Image released June 11, 2012.
CREDIT: China Manned Space Engineering 
I previously wrote about China's plans to build their own space station to compete with the US and Russia. Today, they began the execution of the next phase of their ambitious space plan by launching 3 astronauts to space atop a Long March 2F rocket. The group of taikonauts, which includes China's first woman in space, will perform a docking maneuver with the Tiangong-1 Space Module, and live aboard the miniature space station for a short time, performing experiments. (In case you were wondering, the first woman in space was Soviet cosmonaut Valentina Tereshkova, in 1963. Sally Ride didn't blast off until 1983.)

Apparently, the successful launch elicited cheers from the Chinese control center, where Chinese State Councilor Liu Yandong read an emotional and enthusiastic congratulatory statement from Chinese President Hu Jintao, who effused "I feel very glad to hear the success of launching the Shenzhou 9 manned spacecraft".

In addition to building a space station by 2020, China has previously announced plans to land on the moon by 2016. The US news coverage of this important milestone is funny to read because nearly every article ends with some sort of reassurance from "analysts" that the US is still far ahead of China in the field of space exploration and technology. This instinctive reassurance is humerous but can only mean good things for NASA. If anything can spur public support for the US space program, it's the threat of communism.

Thursday, June 14, 2012

Repurposing a Spy Satellite

On June 4, NASA announced that they have acquired two spy satellites from the National Reconnaissance Office (NRO). The satellites include extremely high quality telescopes with 2.4 meter collection mirrors - the same size as Hubble, and much better quality. For reference, that kind of light-collection power would allow you to see a dime on top of the Washington Monument (or what Kim Jong-un is eating for dinner). The donation is a windfall to NASA's cash-strapped astronomical research program, which will likely turn the impressive optics towards space in the Wide Field Infrared Survey Telescope (WFIRST) project to hunt for dark energy, IF, that is, they can scrape up enough money to launch and commission one of the telescopes. That kind of money may not be available for several years.
The donated satellites have better quality
optics than the Hubble telescope.

It's nice to see where our national priorities lie - as NASA's Planetary Science department literally holds bake sales to raise money and awareness about budget cuts (Obama's 2013 budget cuts 21% from NASA's planetary-science budget, and 38% from its Mars projects,) the NRO has two Hubbles lying around, collecting dust. Of course, we must remember that the NRO deals with very, very important issues of national security, whereas NASA is just playing around with trivial matters of casual public interest, like investigating the mysterious energy that permeates space and accounts for 73% of all matter in the universe.

Sunday, June 10, 2012

Risky Rescue of an Air Force Satellite

Wired had a great article recently about the risky rescue of a malfunctioning Air Force communications satellite. The series of anomalies that occurred are a great example of some of the things that satellite operations teams should be prepared to confront, and made for a very exciting 2 years for the AEHF-1 operations team! First, a bit of background on the satellite, from Air-Force Magazine:
"The AEHF program, one of the largest space programs of the decade, is designed to augment and eventually replace the legacy Milstar satellite communications network. Lockheed Martin is the prime contractor, Northrop Grumman built the payload, and everything is run by Space and Missile Systems Center at Los Angeles AFB, Calif. The constellation of four cross-linked AEHF satellites is expected to provide a communications capacity exceeding that of Milstar by a factor of 10."
The 7 ton, $2 billion satellite, AEHF-1, was launched aboard an Atlas V rocket back in August 2010, and at first it seemed to be functioning perfectly. It was placed into an elliptical orbit about 220 km above the Earth's surface, and the first step in the mission was to fire the satellite's hydrazine engine to booste it into a circular, geosynchronous orbit where it would become part of the Air Force's comms satellite constellation. 
AEHF-1 in the clean room.
Credit: Lockheed Martin

The first sign that something was not right came when the operators first tried to ignite the engine to boost the satellite into geo. Nothing happened. They tried again; the engine did not fire. (In my opinion, firing the engine again was a huge mistake on the part of the operators. As Albert Einstein said, "Insanity is doing the same thing over and over again and expecting different results". In operations, repeating something that didn't work the first time, without first figuring out why it did not work, can mean the end of the mission.) At this point David Madden, the head of the comms satellites at the Space and Missile Systems Center at Los Angeles Air Force Base, stepped in and rounded up a group of engineers who analyzed the telemetry and detrmined that the anomaly was likely caused by a piece of fabric left in the fuel line during the manufacturing process. They also realized that repeated attempts to fire the engine would flood the fuel line and cause the satellite to explode. (Needless to say, they quickly abandoned the "try, try again" tactic.)

With the oxidizer tanks sealed off, rendering the main engine useless, AEHF-1 was stranded in an ineffective and slowly decaying orbit, losing 3 miles of altitude each day.  Compounding the problem was the fact that at its altitude AEHF-1 was sharing an orbit with huge amounts of space junk. Operators were having to fire the small thrusters  in small maneuvers to avoid debris, wasting valuable fuel. 

The operations team was barricaded in a conference room for a week - pizzas were literally slipped to them under the door - and they emerged with a plan to salvage the mission: They would fire the satellite's small thrusters, hydrazine-fueled reaction engine assemblies (REAs) and tiny xenon-fueled Hall Current Thrusters (HCTs). These were originally intended for small orbit adjustments and momentum dumps, but would now be used in a series of more than 450 maneuvers over 14 months to get the satellite into GEO. This would require painstaking planning and precision.

The boosting maneuvers commenced with phase 1 of the recovery procedure: a big orbit-boosting burn to get the satellite out of the danger zone. Very quickly, the second anomaly popped up: The small thrusters required burns that were several hours long in order to be effective, and during these burns the satellite was left with the same side facing the sun, causing components on the sun-facing side to overheat. Overheating can at best diminish mechanism performance, and at worst quickly destroy crucial satellite components. The operations team quickly devised a set of maneuvers to flip the satellite periodically. These maneuvers were inserted during the boosting maneuvers so that no part of the satellite was facing the sun for too long. Flipping the spacecraft, while continuing to keep the thrusters pointed in the right direction and the spacecraft on-target, required an entirely new operations strategy.

Once the schedule of mission-saving maneuvers was in place, operators soon realized that the fuel supply on board was not sufficient to complete the rescue. Every ounce of fuel means another ounce of mass to launch into space (and find space to store onboard the satellite), so the fuel supply is budgeted very carefully based on the minimum mission requirements. Even if AEHF-1 had enough fuel to get to geo, it would still need propellant for station-keeping and momentum management maneuvers once in place, and thus each firing of the minor thrusters meant a shortened mission life. To solve this problem, the software engineers buckled down and re-wrote a chunk of the flight software. The new software allowed operators to position the satellite using the reaction wheels rather than the thrusters, saving fuel. It also optimized fuel consumption in the REA thrusters. The new software was uplinked and implemented successfully.

Engineers calculated the amount of fuel necessary to execute the mission once the satellite was in GEO, and allotted the rest of the fuel to the REA thrusters for the duration of phase 2. When this fuel ran out, the REA thrusters could no longer be used for the rescue effort. At this point AEHF-1  was in the Van Allen radiation belt, a high radiation zone where energetic charged particles are held in place by the Earth’s magnetic field. These particles can damage a satellite's electrical system very quickly, especially the solar panels. This presented a catch-22 for the ops team, because escaping the Van Allen Belt without the REA thrusters would require using the HCT thrusters, which run on electric current. Generating electric current, of course, would require deploying the solar arrays and exposing them to the dangerous radiation of the Van Allen Belt. After much deliberation, the team came up with a strategy to deploy the arrays and fire the thrusters quickly to escape the danger zone with minimal damage.

Once out of the Van Allen Belt, Stage 3 of the rescue continued, with the ops team relying solely on the HCTs to perform the necessary boosting maneuvers. HCTs are generally used for station-keeping maneuvers, and they use electricity and Xenon fuel to emit short, relatively weak puffs of power. However, they can burn for thousands of hours. They had never been used for extended amounts of time in zero G. 
Source: Air-Force Magazine

The HCT motors were optimized to fire at the apogee (the point in the orbit farthest from the Earth) of the AEHF satellite’s orbit, in order to increase the orbit's perigee (the point in the orbit closest to the Earth). (Think of it like a lever - the farther out you push, the more thrust you get).  From late October 2010 to June 2011, the HCTs burned for 10 to 12 hours per day. This required frequent analysis and tuning. Madden described the tedious process: "They’re like a finicky old car, one that you’ve got to constantly adjust to get it to optimize. There’s no instruction manual for how to do that. It’s basically an art."

Once the satellite reached its target altitude of 17,000 miles, the orbit had to be circularized at the correct inclination, which required additional burns to increase the perigree to 22,000 miles, decrease the apogee by 10,000 miles, and drive the inclination down closer to the equator to allow the satellite to see more of the Earth. The ops team timed the burns to take advantage of the beneficial effects of Earth’s gravitational pull, thereby conserving valuable fuel.

Finally, after almost two years, the satellite reached it's target location, and the payload was successfully deployed. Madden says that it still has enough remaining fuel to continue operating for it's full planned lifetime of 14 years. (Of course, this is likely due to the habit of aerospace companies to grossly and purposefully under-predict lifetimes to ensure mission success; with a full tank of gas I'm sure the team was hoping the satellite would last much, much longer.) Nevertheless, it was a remarkable and complex recovery effort. I am sure it was a giant relief to finally deploy the payload, which had been stored inside the satellite in order to fit in the Atlas V launch cone, and see that it worked. Next up: the team will launch and deploy AEHF-2. Best of luck to them, although I bet the operations team is pretty sick of the entire AEHF family at this point.

Summary of Anomalies:

Anomaly 1: Clogged fuel line
Solution: Use REA thrusters to boost orbit

Anomaly 2: Potential Collisions with Space Debris
Solution: Small maneuvers with REA thrusters, and rapid exit from LEO

Anomaly 3: Overheating during orbit-boosting maneuvers
Solution: Periodic spacecraft flips during maneuvers

Anomaly 4: Fuel Shortage
Solution: Re-write/load of the flight software to optimize fuel consumption for new operations plan; Strategic scheduling of burns to take advantage of orbital and gravitational affects.

Anomaly 5: High radiation from Van Allen Belt
Solution: Rapid Solar Array deployment and use of Hall Current Thrusters to quickly boost altitude.