Investigators Cite Design Defect in Intelsat New Dawn Antenna Failure
PARIS — TheNew Dawn satellite launched April 24 has been unable to deploy its C-band reflector antenna, depriving the satellite of half its intended functionality, because the antenna’s spring-loaded deployment mechanism got caught in the billows of its sun shield, according to industry officials briefed on the issue.
A review board investigating the problem concluded that the same phenomenon occurred a month after the launch, when Intelsat and New Dawn’s manufacturer, Orbital Sciences Corp., attempted to deploy the satellite’s Ku-band antenna after abandoning attempts to shake loose the C-band reflector.
During this attempt, the Ku-band antenna’s deployment mechanism also got caught in its sun shield, a thermal blanket that covers the back end of the antenna to protect the satellite from the extreme temperature spikes that occur in orbit.
But unlike the C-band antenna, the Ku-band reflector had a motor-driven deployment mechanism to permit it to be precisely pointed in orbit to maximize customer use. The thinking was — and this is common to many communications satellite designs — that to fine-point the C-band antenna, the satellite’s entire body could be oriented, obviating the need for a second motor.
Using the motor to move the Ku-band deployment system up and down, ground teams were able to free it from the sun shield. Nearly two months after New Dawn was launched, the Ku-band reflector was placed into normal operations and has since been working fine, Intelsat has said.
Luxembourg- and Washington-based Intelsat and Dulles, Va.-based Orbital Sciences have succeeded in reproducing the failure on the ground, confirming the hypothesis.
While satellite structures are extensively tested for fitness in thermal vacuum chambers that simulate the space environment, their antennas are not part of the tests. With antennas deployed, most telecommunications satellites are too big to fit into thermal vacuum facilities.
Orbital has redesigned its sun shield venting, especially for satellites using the company’s larger reflector antennas. New Dawn’s elliptical antennas measure 2.5 meters by 2.7 meters. The redesign includes recalibrating the number and placement of vents in the sun shield to permit trapped air to escape.
It is impossible to rid a satellite of all the air trapped in it. Pockets of air trapped under the sun shield tend to billow in the vacuum of space, and the air is then shed through the vents.
The antennas have four hold-down points, or clamps, which are released on command. The clamps were placed not on the outside of the sun shield but inside it; the clamps released, but the mechanism designed to deploy the antenna got caught in the billowing sun shield.
In an Aug. 4 conference call with investors, Intelsat Chief Executive David McGlade said the Orbital-built Intelsat 18 satellite being prepared for launch in October has been subjected to “corrective actions” to assure the New Dawn issue does not recur. Similar measures are being taken for the Intelsat 23 satellite, also built by Orbital, he said.
The nondeployment of the C-band antenna means Intelsat will need to remove from its contracted backlog all or most of the $310.2 million it had secured for users of New Dawn’s C-band capacity, depending on whether Intelsat is able to find replacement capacity on competing operators’ satellites.
The defect also is expected to cost Intelsat about two years of service life for New Dawn. The company’s attempts to shake loose the C-band antenna in April and May used about a year’s worth of fuel, according to one industry official. The official said New Dawn’s commercial life likely will be cut by another year given the fact that it must be flown in a way that was not planned, with the C-band antenna still tucked against its frame.
Like most modern commercial telecommunications satellites, New Dawn was expected to operate for 15 years in geostationary orbit.
In an Aug. 5 response to Space News inquiries, Orbital issued the following statement:
“We’ve investigated the New Dawn situation with our customer Intelsat and understand why the antenna did not deploy. With that knowledge, we have designed and implemented corrective measures to ensure that it does not happen again.”
Responding to Space News inquiries, Intelsat on Aug. 4 issued the following statement:
“The Intelsat New Dawn failure review board completed its investigation and concluded that the deployment anomaly of the C-band reflector was most likely due to a billowing of the reflector sun shield.
“The billowing caused the sun shield to capture the ejection-release mechanism and prevent reflector deployment.”
Intelsat officials have not abandoned all hope of freeing the stuck C-band antenna. In several weeks, New Dawn will enter a period of eclipse, causing a sharp change in thermal environment that might be able to accomplish what could not be done with the previous shaking attempts.