The importance of software is often underestimated, but
its development is a large aspect to
successfully running a system of machines as complex as the TMT. In fact, it is critical that software designed for such a
system is designed upfront. As a result, the software development for
the TMT is moving in step
with other hardware design projects.
Software is integral to both the organizational and technical aspects of the TMT's operation. Organizationally, astronomers must submit proposals for observations
which, if approved, are then carried out and the data is processed and stored in a scientific data archive. Each step of the
controlled with computers running software specifically designed for the project. In addition, since nothing like
has been built before, it will require new software to control the mechanical aspects of the
telescope: from opening and closing the telescope's enclosure to the fine movements of the adaptive optics system. Without the corresponding software, the mechanical
aspects of the telescope would be useless.
Software for TMT is being developed by a small group at the National Research Council Herzberg Institute of Astrophysics
(NRC-HIA). Since the subsystems being designed for
the TMT are interdependent and will ultimately work together,
software developers often attend hardware meetings. This is
advantageous in that software design can be simplified
and it will be easier to integrate all the instruments in the long run. There is no benefit to quick
fixes with software; getting things right and working smoothly the first time saves both time and money.
The development of this software is also a very challenging project
for the TMT as it is very complex. Take the control of
the primary mirror for example - in the VLOT design specifications, with the exception of the
edge cells, each primary mirror cell has 6 sensors gathering information about its placement relative to
the ones around it. With 150 mirrors, that means a computer must be able to process and make sense of
information being gathered by a little less than 900 sensors. In comparison, the TMT design calls for
over 500 mirror segments and will require a similar but
faster system to control the primary mirror. This system is only
one of many that will be used to control the telescope for a
given observational session and they must all work
together seamlessly in order for the TMT to be effective.
The telescope is designed to operate in two modes; the classical and queued observing
modes. Each one
is currently expected to be used 50% of the time. Classical observing
refers to those cases when a telescope operator or
observer physically attends the night of observing. They have a list of objects they would like to observe, and
can move the telescope about at their leisure. The advantage to this is that in poor conditions, an
observer has the option of totally changing what they planned to do that night, or chase patches of clear
sky that they might not have been planning on using. In
contrast, queued mode involves automated observations which
orders a list of observations from a database of prioritized requests and
then carries them out.
The telescope will be equipped with sensors so that in
queued mode the enclosure will not be opened in conditions that
could damage the instrument; however, queued mode lacks the creativity that an individual brings to an
observing night. Furthermore, in queued mode the observer does not have to be present to obtain their required
data, cutting travel costs, increasing the time efficiency
of the telescope's usage and frees up time for the
individual to do something else, such as data analysis.
These are just some of the challenges involved in developing software for what will be the world's largest
telescope. It demands things on a scale never done before and will result in the development of new,
cutting-edge programs that will likely influence observatory software design for years to come.