MER in ATLO: SOME ASSEMBLY REQUIRED
The beginning of a race often starts with the words "On Your Mark! Get Set! Go!" If the Mars Exploration Rover mission were to be compared to the beginning of a race, ATLO (Assembly, Test and Launch Operations) would be the part where the starter yells "Get Set!" Even though no one has said these two words, they were heard loud and clear by hundreds of scientists, engineers, and technicians on February 25, 2002. That's when the MER Project moved into ATLO.
ATLO is the last step before launch - and it is a big one. During ATLO, each MER spacecraft is assembled, tested, calibrated, and delivered to the launch pad. It is a well-organized, well-documented process that takes more than a year to complete.
Thousands of individual parts are delivered to the Spacecraft Assembly Facility at the Jet Propulsion Laboratory in California where they are tested and meticulously assembled. Electronics boards, switches, cables, wires, sensor heads, batteries, cameras, antennas, motors, gearboxes, solar panels, airbags, parachutes, and lander petals are a few of the components that will mesh together to become two MER spacecraft.
But before rover assembly can begin, individual "subsystems" must be tested. These include the instruments, which have undergone extensive testing before they reach JPL, but still they must pass detailed reviews to prove they are rover-ready. All the cameras that the rovers will carry -- Pancams, Navcams, Hazcams, and Microscopic Imagers -- must be calibrated. That's nine cameras per rover for a total of 18 cameras. It's a painstaking process of observation and record keeping.
Once the rovers are built and all the science instruments are integrated, more tests are conducted on the complete system. Engineers want to be certain that each instrument will "talk" to the rover and that they will exchange commands and data. Hardware and software are checked and rechecked for any anomalies. Science instruments are aligned with one another, so that data from one instrument can be co-registered with the data from another instrument.
The MER spacecraft must also undergo a series of environmental tests. These are tests that expose the rovers to the type of environments they will encounter from launch here on Earth to landed operations on Mars. Vibration tests simulate the rigors of liftoff. Solar-thermal-vacuum tests immerse the spacecraft in temperatures and pressures they will see on their way to Mars and on the Martian surface. Electromagnetic interference (EMI) tests make sure that one piece of hardware does not cause an electrical interference for another piece of hardware. All the instruments are operated separately and then together to check for any stray electromagnetic signals.
Then there are tests of the electrical system to make sure circuits and cables are operating smoothly so that the spacecraft can be heated, powered, and commanded. And there are tests of the mechanical systems on the rover, lander, aeroshell, and cruise stage.
The final phase of ATLO is the "launch operations." This phase not only prepares the MER for its journey into space via a Delta II rocket, but involves all the necessary safeguards that must be taken for a much shorter trip - the journey across the United States from the SAF in California to the launch pad at Cape Canaveral, Florida.
Web content editor/writer: Pamela R. Smith
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