TacSat-2: A Story of Survival

With the launch of TacSat-2, the Operationally Responsive Space (ORS) program has its first on-orbit asset and the ORS community finally gets an opportunity to transition from talking about the benefits of responsive space to demonstrating them. TacSat-2, however, is far from a pure ORS spacecraft and its relevance and utility is far from restricted to the ORS arena. The spacecraft that became TacSat-2 had its origins in a formation flying program called TechSat-21. Though the TechSat-21 program was cancelled, much of the basic spacecraft design survived and reemerged under the name of Roadrunner. Roadrunner was supposed to demonstrate how a militarily relevant spacecraft could be developed and fielded on an accelerated timeframe. It was under-funded from the start and the mission architects solved the financial problem by entering into a number of military, civil, and commercial partnerships. Unfortunately, each partner brought more than money and advocacy -- they brought their own sets of experimental hardware and the associated requirements. When the ORS program saw many commonalities between Roadrunner’s objectives and their own, they adopted the spacecraft as part of the TacSat ORS program, bestowing upon it additional prestige and the opportunity to become an operational military asset, but further increasing the growing list of mission requirements. When it was all said and done, TacSat-2 was a spacecraft that had to carry thirteen payloads to orbit (many of which doubled as essential, non-redundant subsystems) and fulfill about 140 on-orbit mission requirements. It had tactical sensors, two innovative new communication links, experimental solar arrays, star cameras, and propulsion systems, as well as payloads designed to answer basic scientific questions, such as how atmospheric density and RF signal interference fluctuates with local and remote environmental conditions. Moreover, it had to accomplish its mission on a shoestring budget and under the severe schedule pressure inherent to the Responsive Space movement. The TacSat-2 story is truly a story of survival in the low-budget, high-expectation R&D spacecraft world. The mission successes have been significant and ground-breaking, but they have, almost without exception, been compromised successes. You will see a spacecraft that wasn’t developed within a year of program initiation (a primary ORS program objective), but it created an integrated test and ground system/operations development strategy that makes that goal more attainable. You will see a spacecraft that wasn’t integrated onto its launch vehicle, launched, checked out, and ready for full operation within a week of notification (another primary ORS program objective), but demonstrates remarkable on-board autonomy that might enable that on a less complex spacecraft. Finally, you will see a spacecraft who’s on-orbit performance is sometimes disappointing and sometimes remarkable, but steadily achieving almost all of its on-orbit tactical and scientific objectives