Several scientific areas in which Canadian scientists enjoy world leadership can be advanced tremendously by relatively small, inexpensive spacecraft that are dedicated to a single purpose. A small payloads program provides the only mechanism for Canadian scientists to develop these ideas into real projects. These missions maintain and enhance Canada’s scientific leadership and reputation in specific areas of astronomy and provide a natural mechanism to train young scientists in the science and technology of space astronomy. In some cases they play a role as a stepping stone to establishing scientific leadership in key areas of the proposed major international mission component of the space astronomy program.

We propose a program of concept studies, phase A design studies, and following a peer review assessment fabrication, launch and operation Currently there are four proposed missions that could form the bases of this program in the near term. All represent unique investigations with high scientific value. Some have already advanced to the concept study phase.

SCIX: A Silicon Coded – Mask Imager for X-rays. Proposed by Leahy et al., the scientific payload would be a hard x-ray imaging instrument. SCIX would carry out a high sensitivity all-sky survey for hard x-ray emission (3 - 40 keV photon energy). The target cost of the mission excluding launch is 10$ - 20$ M, with a payload mass of 100-200 kg and an in orbit lifetime of 2- 3 years. At its projected sensitivity, SCIX would detect about 5000 discrete sources of emission (compares to a few hundred for the best previous survey mission HEAO-1). The mission would uncover new sources of x-ray emission both within our galaxy and from the extragalactic universe.

CUVIT: The Canadian UV Imaging Telescope. Proposed by Rucinski et al., this mission would consist of a wide-field ultra-violet imaging camera to operate in the wavelength range (120 – 300 nm). With one arcsecond pixels and images 2000x2000 on a side it would be capable of imaging a 0.5 degrees fields. A concept study for this mission has already been carried out. It would provide unique images of hot young stars, providing new insights into massive star formation and evolution and the energization of the interstellar medium.

MOST: Microvariability and Oscillations of Stars. This microsat mission proposed by Matthews et al. would be a 10-15 cm telescope with twin CCD detectors placed in a Sun-synchronous orbit. Its planned one-year mission would be to monitor up to six field stars or clusters with high photometric precision and time resolution. This mission represents a frontier in space astronomy where Canada can easily assume a leadership role. The field of asteroseismology (stellar seismology) is a rapidly burgeoning field in which Canadian scientists are top in the field. This technique allows the interiors of stars to be probed via their rapid surface vibrations. By placing a small telescope above the atmosphere, MOST currently represents the best prospect to make the first detection of acoustic oscillations in another Sun-like star - a prized goal of solar and stellar astronomers worldwide.

CCS: The Canadian Carbon Surveyor proposed by Taylor et al. This mission represents a component of the Canadian Galactic Plane Survey (CGPS) project being carried out by a consortium of over 30 Canadian scientists. The proposal is to launch a one or two year mission to obtain 3-dimensional images of the Milky Way Galaxy and other nearby galaxies in the far-infrared emission line of the Carbon II transition at 158 m m. The [CII] emission line is the prime coolant of the interstellar medium but is unobservable from the ground. In combination with atomic hydrogen data from the CGPS, the CCS data would allow an unambiguous discrimination of the phases of the diffuse interstellar medium, provide a 3-D image of the cooling rate and pressure on the galaxy. The data are critical to understanding the physics of the formation of molecular clouds from diffuse gas – one of the key physical processes that must be understood in interpreting data from the early Universe, as will be provided for example by the FIRST mission.

This class of Canadian-lead mission has obvious and direct benefits:

• The creation of fundamental knowledge in key areas of astronomy,
• training of highly qualified personnel for the capacity to conduct and to manage research and technology,
• maintaining and enhancing the interface between public and private sector research and development,
• contributing to Canada’s reputation and prestige in science and space technology.

It seems clear that the scientific interest within the astronomy community appears capable to support up to one mission per year in this small-mission category. We propose on average one micro-satellite or rocket mission (total cost < ~ $4 M) every two years and one sci-sat class mission every third year ($10-$20 M). Total program cost would be on average ~ $7 M/year. During the period 1997 – 2000 concept studies and phase A design could carried for all of the four proposed missions, followed by launch and operation up to about 2004. These missions provide an excellent lead up to launch of the proposed international partnership missions NGST and FIRST/Planck in the 2005-2010 period.