Michigan Aerospace Corporation - Autonomous Satellite Docking System (ASDS)

ASDS - Autonomous Satellite Docking System


	AMDS Docking Sequence (Patent Pending)

Program Directive Develop the technology for an on-orbit demonstration of autonomous rendezvous and docking of two satellites to enable fluid/gas re-supply and payload exchange.
	Program Manager Anthony Hays anthonyhays@michiganaerospace.com (734) 975-8777 x111
Program Sponsors / Affiliates DARPA Phase I SBIR DARPA Phase II SBIR

Project Applications:
The development of autonomous satellite servicing systems potentially has a wide range of uses in both military and civil space programs. Obvious applications in the military markets include re-fueling of surveillance and reconnaissance satellites as one means to increase both their lifetime and utilization factor. In the civil space sector, a similar need exists to refuel operational systems that are fuel limited but whose data is essential (e.g., communications, navigation, weather satellites).

ASDS is MAC's Solution for DARPA's Orbital Express Space Operations Architecture
DARPA's Orbital Express Program intends to develop and demonstrate autonomous satellite capabilities including re-fueling and on-orbit satellite reconfiguration. For more information, take a look at DARPA's Orbital Express website.

Advantages of ASDS versus Current Technology:
The cost of building and launching satellites limits the number of assets that can be placed in orbit. This makes it critical for the asset to have as long a lifetime as possible to reduce the replacement rate. The primary limiting factor of satellite on-orbit lifetime is its ability to maintain a useful, stable orbit, which in turn is limited by on-board fuel at launch. There is also a growing requirement to give satellites the ability to maneuver to new orbits on a regular basis, including expensive plane changes. The ability of a satellite to change orbits on a regular basis makes it less vulnerable to attack, allows it to be repositioned to observe new crisis areas, and reduces the need for multiple-satellite constellations to provide global coverage. This comes down to the amount of fuel the satellite can carry to allow orbit maneuvers and pointing changes. Since the amount of fuel that a satellite can carry is limited by launch costs and weight limitations, the ability to re-fuel a satellite on-orbit is the only method available to increase its useful lifetime.

Satellite lifetime is also determined by failures of critical components. If satellites were made to be serviced, it should also be possible to "repair" the satellite using an automated payload-exchange system to replace the damaged unit. In the past, several groups have looked at the problem of making satellites more serviceable. Re-fueling or repairing satellites using the Space Transportation System (STS - Space Shuttle) is cost prohibitive, limited in terms of the orbit range of the STS, and unnecessarily involves the use of astronauts. The Autonomous Satellite Docking System (ASDS) would allow autonomous or semi-autonomous on-orbit servicing without the use of STS.

Project History:
In 1993, a low Earth orbit (LEO) demonstration for Autonomous Rendezvous and Docking (ARD) was developed at the Space Automation and Robotics Center (SpARC) and provided a near-term option for validating many of the enabling technologies and concepts required for satellite resupply and servicing. Flight hardware currently exists in the form of a target spacecraft payload intended for a small satellite. The hardware includes a docking mechanism, sensor targets, avionics, gas and payload resupply interfaces for the target spacecraft, as well as a prototype of the docking system for the chaser spacecraft. The on-orbit demonstration was intended to validate that technology existed for performing autonomous rendezvous and docking that could lead to propellant resupply for satellites, fluid/gas re-supply for orbiting laboratories, and payload exchange for satellites or servicing missions.

Michigan Aerospace Corporation has developed a mechanism for micro satellite docking, which has been successfully demonstrated in a microgravity environment. This docking mechanism is specifically designed for soft-docking capability, tolerance to misalignment, and scalability. The current Autonomous Micro satellite Docking System (AMDS) design resulted from modifications to an earlier docking mechanism prototype that was tested at the Marshall Space Flight Center (MSFC) Flat Floor Facility.

Autonomous Micro Satellite Docking System (AMDS):

The AMDS was tested in a microgravity environment through the NASA JSC Reduced Gravity Program, under funding from the Air Force Research Laboratory's Space Vehicles Directorate (AFRL/VS), Microcosm, Inc. and Spectrum Astro. The Reduced Gravity office operates a KC-135 aircraft that flies a series of parabolic zero-g maneuvers. The test objectives of the KC-135 flight were to determine the docking mechanism cable assembly behavior in zero-g, test the full range of the docking envelope in a six degree of freedom test setup and determine the undocking capability and stability. The nature of the Michigan Aerospace docking mechanism enabled the entire docking cycle, including soft dock, auto-alignment and hard dock, to be completed within the 20 seconds of 'zero-g' time. Complete end-to-end docking and undocking was performed under a variety of initial conditions and docking parameters. The data collected during the KC-135 testing will be used to validate dynamic simulation models of the docking mechanism. The intent of these dynamic models is to examine a number of docking scenarios between a chaser and target satellite. The results are described in the following papers: