BOSTON — The U.S. Air Force is taking careful note of a variety of headaches experienced thus far with the TacSat-2 experimental spacecraft in hopes of avoiding similar problems on future TacSat missions, a program official said. The problems have included technical glitches, launch preparations that took far longer than anticipated, and a policy dispute that has held up activation of the satellite’s two main instruments .
Despite their frustrations, Air Force officials overseeing TacSat-2, launched Dec. 16, described it as a “growing success story” during a Feb. 16 briefing for Gary Payton, deputy undersecretary of the Air Force for space programs.
Neal Peck, TacSat-2 program manager at the Air Force Research Laboratory’s Space Vehicles Directorate at Kirtland Air Force Base in New Mexico, and Chuck Finley, chief of operations at the directorate , said in briefing charts that they were making “excellent progress” in meeting TacSat-2’s goals and “learning a tremendous amount.”
TacSat-2 is the first in a series of satellites intended to give the U.S. military experience with inexpensive space assets that can be built quickly, launched on short notice and be directly controlled by commanders in the field. The satellite has 13 payloads, the primary ones being an optical sensor and a signals-intelligence receiver.
Mission managers have encountered a number of technical snags, which is not all that unusual in the early operations of experimental satellites. But they’ve also been wrestling with a policy problem in the form of concerns that the spacecraft could be perceived as an instrument for spying, possibly on U.S citizens. Because of those concerns, Peck said March 6, the Office of the Secretary of Defense has withheld its approval for activation of TacSat-2’s imaging and signals-intelligence payloads.
Maj. Patrick Ryder, a spokesman for the Office of the Secretary of Defense, said March 9 that the policy issue had been resolved and that the only thing standing in the way of using the sensors was a problem with TacSat-2’s downlinks.
But a Pentagon source subsequently offered a slightly different version of events, saying that while senior defense officials had recently approved the sensors’ activation in principle, they also directed mid-level staff to hammer out an agreement on TacSat-2 operations that would avoid the appearance of domestic spying. At press time, that agreement was still pending and the sensors were not cleared for operations, the source said.
The downlink issue, this source said, stems from the use on TacSat-2 of the Common Data Link, which was designed for air-to-ground communications. The system has never been used before for satellite-to-ground links, and TacSat-2 mission managers were only getting limited contacts with the satellite via the Common Data Link during each 10-minute pass, the source said.
Connie Rankin, a spokeswoman for the Air Force Research Laboratory, said March 15 that the Air Force has made software changes to correct the problem and was in the process of verifying that they were successful.
Meanwhile, operating the spacecraft and its other instruments has kept program officials plenty busy.
Managers have been pleased thus far with their ability to command the satellite and receive data via a mobile ground station in California, according to the briefing charts, copies of which were provided to Space News . Data from the satellite has been autonomously sent from the ground equipment to an online data center, where it is available to TacSat-2 users, according to the charts .
The satellite has been able to automate functions typically handled by Air Force personnel, Peck said.
Other positives noted on the charts include successful operation of Hall- effect ion thrusters designed by Busek Co. of Natick, Mass., that are intended to demonstrate more efficient in-space propulsion than conventional chemical thrusters, according to the charts .
However, the mission also has encountered its share of technical difficulties , starting with a ground-system problem that left controllers unable to contact the satellite for several days immediately following the launch. While this caused program officials to miss their goal of having TacSat-2 all checked out within a day of launch, they still intend to demonstrate that capability by shutting down the satellite’s systems and then restarting them as though it had just reached orbit, Peck said.
Pointing accuracy also has been a problem . Controllers have at times found a pointing error of about 2 degrees, which can put the spacecraft’s sensors off by as much as 20 to 30 kilometers with respect to ground targets, Peck said. This could result in them missing these targets entirely, he said.
Program officials are planning to upload software that they hope will correct the problem, Peck said.
Other problems have resulted from what program officials now believe was the inclusion of too many payloads on the satellite, Peck said. TacSat-2’s main computer has become overloaded at times, causing it to shut down and disrupting operations for a day. Finding time to experiment with each of the instruments also has proved difficult, he said.
Future TacSat satellites will carry far fewer payloads than TacSat-2 , he said.
TacSat-2 also has provided important lessons in launch preparation. TacSat-2 was launched aboard a Minotaur rocket from NASA’s Wallops Flight Facility, Wallops Island, Va.
One of the program goals was to demonstrate that tactical military satellites can be launched within six days of a formal request from Pentagon brass. But Orbital Sciences Corp., the Dulles, Va.-based Minotaur contractor, used a single team to make the final launch preparations and the process took three weeks, Peck said.
The single-team approach was intended to eliminate the possibility of potential problems being overlooked as a result of a personnel changeover from shift to shift, Peck said. While acknowledging the value in that approach, he said the Air Force needs to find a way to do around-the-clock preparations to support six-day launch cycles.