Thursday, October 8, 2009 – 6:21 p.m. — 51.6°F
In just a few hours, two spacecraft will be intentionally crashed into a polar crater on the moon. NASA’s LCROSS (Lunar CRater Observation and Sensing Satellite) mission plans to plunge a Centaur rocket into the surface while a second spacecraft follows 4 minutes behind on the same track. The trailing craft has cameras and instrumentation to observe the debris plume, expected to contain 250 tons of material, produced by the first impact. The sensor craft will continue imaging and analyzing as it follows through the plume until it also crashes into the lunar surface. The current projected time for impact of the first craft is tomorrow morning, at 7:31 a.m. EDT. Oh, and 19 seconds, just in case you thought NASA didn’t know.
Drawing of the Centaur rocket, LCROSS, and LRO, prior to LRO separation.
The rocket being used as the rock in this mission isn’t just a throw-away patsy. It has already performed a great mission, as this particular Centaur not only launched the LCROSS craft, but also carried the Lunar Reconnaissance Orbiter into space last June 18. After an Atlas V rocket provided most of the boost and dropped off, the upper-stage Centaur rocket completed the initial launch, refined the orbit, shut off and coasted for 23 minutes, and then re-ignited over the Indian Ocean for another burn of 4 minutes 55 seconds. When this last boost ended, the spacecraft was still at an altitude of only 200 nautical miles, but the Centaur had provided enough boost to send everything on its way to the moon. Less than 3 minutes later, now at an altitude of 400 nautical miles, the LRO orbiter separated from the LCROSS satellite and the Centaur, and began its independent mission. Four and a half days later, on June 23, LRO entered its initial lunar orbit. It has since been adjusted to a finalized low orbit and has been snapping pictures like crazy ever since, providing the best resolution and overall coverage ever yet obtained for the moon. So, as I said, the Centaur rocket has already done a great job by successfully delivering LRO.
LCROSS orbit viewed from along the ecliptic.
Meanwhile, though, after LRO had separated, LCROSS was also on its way to the moon, but with quite a different outcome. Instead of going into lunar orbit, LCROSS swung around the moon and entered a highly elliptical 37-day polar orbit around Earth. For almost 4 months now LCROSS has slowly worked its way around the planet. But there’s a trick in store. On one of those orbits, LCROSS intersects the moon.
So where does the Centaur come into this story?
A Centaur-D1 rocket, which will be staged above a Titan-3 rocket.
A Centaur rocket operates out of the public eye, and many fans of space research and projects will never have heard of it or be aware of its contributions to the missions they’ve watched over the decades. The Centaur is always used as an upper stage rocket, providing the final boost to a mission. Centaurs insert and refine orbits, boost satellites from low-earth orbits to higher or geo-stationary orbits, or provide enough power for a craft to achieve escape velocity and leave earth orbit entirely. When the full rocket assembly sits on the pad, individual units mated into one sleek unit, you don’t notice the Centaur stage. When the rocket blasts off and people ooh and aah, watching it roar and disappear into the sky, they don’t see a Centaur firing. They’re watching an Atlas or Titan missile launch. The Centaur ignites later, out of view of the public.
And usually, that’s it. Having provided the power, and done so in a precise direction, a Centaur rocket separates from the “important” part of the launch unit and is forgotten, done with its work.
But not the LCROSS Centaur. Instead of separating, for this mission the Centaur has stayed attached to the LCROSS craft. It will separate only during final approach, 9 or 10 hours before impact, and then take its position on center stage. When it slams into the Cabeus crater near the moon’s south pole, Centaur will finally be a public star.
It’s about time. Since 1965, Centaur rockets have powered lots of great missions, but to little fanfare. This is one of the oldest basic rocket designs still in use, and with a few modifications over the years to size and number of rockets, to fit various mission needs and booster missiles, it is one of the most versatile. Centaurs have ridden atop several versions of Atlas rockets, as well as the Titan 3E and Titan 401A and 401B rockets. In 188 launches Centaur has had only 13 failures, and 5 partial failures where an improper orbit was achieved but part of the mission goals could still be met.
Centaur’s missions over the years? Well, you might recognize one or two . . .
1960’s
Surveyor 3 on the moon, with the Apollo 12 lunar lander visible behind it on the horizon.
all of the Surveyor series of unmanned moon landings (Surveyors 1 through 7; 5 missions landed successfully, while Surveyor 2 and Surveyor 4 crashed into the lunar surface, no fault of the Centaur!)
the Stargazer Orbiting Astronomical Observatory (OAO-2)
Mariner 6 and Mariner 7 (Mars fly-by instrumental missions)
6 other earth-orbit satellite launches
1970’s
Mariner 9 (Mars orbital photography mission) and Mariner 10 (Venus and Mercury fly-by instrumental mission)
Pioneer 10 (asteroid belt fly-through, Jupiter fly-by, and headed out of the solar system toward Aldebaran)
Pioneer 11 (Jupiter and Saturn fly-bys, and continued out of the solar system)
Pioneer 12 (Venus orbiter) and Pioneer 13 (Venus mission with 5 separate probes sent down through the atmosphere)
Viking 1 and Viking 2 (Mars missions, each consisting of both an orbiting sensor/communications unit and a landing unit)
Helios 1 and Helios 2 (both placed in close heliocentric orbits for solar studies)
the Copernicus Orbiting Astronomical Observatory (OAO-3)
HEAO 1, HEAO 2 (the “Einstein” observatory), and HEAO 3 (3 different High Energy Astronomy Observatory missions, with X-ray and gamma ray experiments and telescopes)
Neptune, showing the Great Blue Spot, photographed by Voyager 2.
Voyager 1 (Jupiter and Saturn fly-bys, eventually left the solar system, still transmitting data from experiments and may continue to do so until 2025)
Voyager 2 (fly-bys of Jupiter, Saturn, Uranus, and Neptune, and continued on out of the solar system, also expected to transmit data until 2025)
17 other earth-orbit satellite launches (12 INTELSAT, 3 COMSTAR, and 2 U.S. Navy FLTSATCOM satellites)
1980’s
17 earth-orbit satellite launches (10 INTELSAT, 1 CONSTAR, and 6 U.S. Navy FLTSATCOM satellites)
1990’s
CRRES (Combined Release and Radiation Effects Satellite, which studied fields and particles within the Earth’s magnetosphere)
GOES 8 (served in the GOES-EAST position), GOES 9 (served in the GOES-WEST position), and GOES 10 (currently in the GOES-SOUTH position) (U.S. Weather Service Geostationary Operational Environmental Satellites)
SOHO (SOlar Heliospheric Observatory)
SAX (Satellite Astronomia Raggio-X, an Italian X-ray observatory)
Saturn viewed from above by the Cassini orbiter.
Cassini-Huygens (combined probe and orbiter, with fly-bys of Venus [twice], an asteroid, and Jupiter, before settling in to orbit Saturn. Cassini continued orbiting Saturn, while the Huygens probe descended through Titan’s atmosphere)
Terra (EOS-AM-1, part of the Earth Observing System series, monitoring climate and the environment)
52 other earth-orbit satellite launches (10 U.S. Navy UFO, 6 U.S. Military DSCS, 6 INTELSAT, 3 U.S. Intelligence Trumpet, 3 JCSAT, 3 Galaxy, 2 MILSTAR, 2 U.S. Intelligence Mentor, 2 U.S. Air Force Mercury, 2 GE, 2 EchoStar, 2 INMARSAT, 2 EUTELSAT, 1 DirecTV, 1 Palapa, 1 U.S. Reconnaissance SDS, 1 HotBird, 1 Orion, 1 Tempo, 1 SuperBird, 1 AMSC, and 1 TELSTAR satellites)
Current Decade
GOES 11 (currently in the GOES-WEST position) and GOES 12 (currently in the GOES-EAST position) (U.S. Weather Service Geostationary Operational Environmental Satellites)
TDRS 8, TDRS 9, TDRS 10 (Tracking and Data Relay Satellites, used to communicate with space missions and the space station)
NOSS-3 1A/1B, NOSS-3 2A/2B, NOSS-3 3A/3B, NOSS-3 4A/4B (Naval Ocean Surveillance System, 4 launches, each of 2 satellites)
Mars Reconnaissance Orbiter (instrumental mission in Mars orbit)
New Horizons (currently en route for flybys by Pluto and its moons)
CFEsat (Cibola Flight Experiment Satellite, instrumentation for VHF and UHF ranges, for ionospheric and lightning studies)
ASTRO/NextSAT (experimented with automated refueling and reconfiguration of satellites)
LRO/LCROSS (our heroes of the day! read above for info)
36 other earth-orbit satellite launches ( 4 U.S. Reconnaissance SDS, 3 MILSTAR, 3 AMC, 2 U.S. Military DSCS, 2 HISPASAT, 2 ICO, 2 U.S. Military WGS, 2 EchoStar, 1 U.S. Intelligence Trumpet, 1 EUTELSAT, 1 HotBird, 1 AsiaSAT, 1 HellasSAT, 1 Rainbow, 1 U.S. Intelligence MENTOR, 1 U.S. Navy UFO, 1 MBSAT, 1 InMarSAT, 1 Astra, 1 FALCONSAT, 1 MIDSTAR, 1 STPSAT, 1 SuperBird, and 1 U.S. Surveillance PAN satellites)
Pretty impressive list, huh? Next time you hear a weather forecast, or use a telephone, or watch television, or marvel at some astronomical wonder, remember that there’s a pretty good chance that a Centaur rocket was involved somehow in bringing you that moment. And let’s hope all goes well and tomorrow morning a Centaur makes a big splash and finally gets some recognition it deserves.
