CanX Program
CanX-1
CanX-2
CanX-3 - BRITE
CanX-4 & CanX-5

Historically, planetary exploration has been performed using large, complex, and costly spacecraft that have attempted to bring a laboratory of instruments with them. Only in the early days of the American and Russian space programs were the missions less complex and more focused. The Canadian Robotic Asteroid Flyby and Tentatively Impact (CRAFTI) mission proposes to return to some of the philosophies of that era, and to bring modern microsatellite design philosophies into planetary exploration.

The CRAFTI mission is a concept study being undertaken by the University of Toronto Institute of Aerospace Studies Space Flight Laboratory (UTIAS-SFL) and the Canadian Space Society, with funding from the Canadian Space Agency and technical support from Dynacon Incorporated. The study is aimed at proving that microsatellite technology can, and should, be applied to planetary exploration. The principal investigator is Dr. Kimmo Innanen of York University, and the lead engineer is Henry Spencer of UTIAS-SFL. The target of this project is a Near Earth Asteroid suitable for a relatively slow flyby, tentatively chosen to be Toutatis during its 2008 closest approach with the Earth. Asteroids present the best target for such a mission, as they offer the greatest possible science return for relatively simple instruments and relatively low mission cost. In addition, a flyby during closest approach turns out to be a surprisingly easy mission.

The CRAFTI mission presents an opportunity to prove that microsatellite technology has come of age, not only in Earth orbiting spacecraft, but also in the realm of planetary exploration. The key to success is a careful tradeoff between available spacecraft resources and mission design, and having on board only what is absolutely necessary for the mission to succeed.

Perspective

Traditionally, planetary exploration missions cost hundreds of millions, or even billions, of dollars. For instance, the Cassini spacecraft now on its way to Saturn has an estimated total program cost of US$3.3 billion. Even NASA's Discovery program, which emphasizes lower costs, typically costs $100M or more per mission. Lunar Prospector, the first Discovery mission, was considered an outstanding bargain at approximately $63M. More recent Discovery missions have all been more expensive. The Canadian Space Agency could afford expenditures even at the comparatively modest Discovery level only as part of a major policy initiative, which seems politically unlikely. At first glance, the cost alone would seem to preclude independent Canadian planetary exploration missions. Upon closer examination, however, this is not the case. The Microvariability and Oscillations of Stars (MOST) microsatellite, with a budget of approximately CDN$6M, could almost operate in deep space. It would need small adjustments to engineering details, plus:

• An attitude control system (ACS) less dependent on Earth's magnetic field (star sensors and thrusters instead of magnetometers and magnetorquers).
  
• Longer communications range (high-gain antennas and greater transmitted power).
  

This would complicate the design, but the cost increase would be modest. This suggests that deep space spacecraft need not be costly.

Deep Space Missions

Merely being able to operate in deep space is not sufficient to conduct a planetary mission. Also required are:

• A launch and subsequent maneuvers sufficient to reach the target.
  
• Trajectory corrections to encounter the target in the intended manner.
  
• Instruments capable of returning useful science data from the encounter.

These issues present somewhat more substantial problems, but not so severe that they are beyond low-cost solutions, provided the mission is chosen with care and restraint. Small spacecraft cannot do every planetary mission. But with careful balance, planetary exploration is not beyond the reach of the microsatellite approach, and at microsatellite price tags. There are some constraints. Planetary exploration on a microsatellite budget appears possible if:

• Spacecraft design is optimized for low-cost, available launching solutions.


• Small-scale propulsion is developed to flight readiness.


• Targets and missions are chosen with cost in mind.


• Restraint is exercised in choice and development of science instruments.


• Microsatellite philosophy is applied throughout and existing design heritage is maximized.


• An experienced team performs the required work.


• Project work is completed at a fast pace to avoid the extra overheads of lengthy programs.

The CRAFTI Concept

Thus, the Canadian Robotic Asteroid Flyby and (Tentatively) Impact (CRAFTI) concept. CRAFTI is a Canadian Space Agency (CSA)-sponsored concept study for an all-Canadian planetary mission on a microsatellite budget. The target cost is under CDN$20M (approximately US$13M) including launch and operations. The spacecraft concept uses MOST technology wherever possible, developed by the MOST team at Dynacon and UTIAS-SFL. The mission involves a flyby of a near-Earth asteroid as the asteroid passes near Earth., and is implemented using two secondary launches. To enhance mission reliability, CRAFTI proposes to revive a venerable NASA custom: launching two identical spacecraft for each mission. Building and launching a second identical spacecraft is relatively inexpensive, and it provides excellent insurance against mission loss due to component failure, operations error, or launch failure.

One question that arises, then, is given two spacecraft, what extra science can be performed if both spacecraft succeed in arriving at the target? If this occurs, one spacecraft will be tasked with the primary mission flyby, while the other spacecraft will attempt an impact. The impacting spacecraft can perform science, including imaging, at very close range, and the observations of the impact from the flyby spacecraft will yield information about the structure of the outer layers of the asteroid.

CRAFTI and MOST

The MOST project is currently demonstrating that a small astronomy satellite can be built and flown for a total cost (excluding launch) of ~CDN$6M (US $4M). Much of the design heritage for CRAFTI comes from the MOST hardware. Many components on the MOST system can be reused, with modification, in a spacecraft such as CRAFTI. While new subsystems are needed, and some need to be largely redesigned (for instance, the radio subsystem), the reuse of this hardware will help make CRAFTI inexpensive. Additionally, the experience gained by the UTIAS-SFL team in building and operating MOST and other planned microsatellite projects provides an excellent experience base for building and flying CRAFTI.