The Secondary Mirror System (M2S) and Tertiary Mirror System (M3S) of the Thirty Meter Telescope (TMT) consist of
passively mounted mirrors supported in kinematic cell assemblies that are moved during telescope tracking to counteract
effects of changing zenith angle and thermal gradients within the telescope structure. TMT is concerned that the
requirements for pointing jitter during Adaptive Optics tracking for the M2 and M3 Systems are very challenging with a
risk of requiring complex stabilization systems for compliance. Both systems were researched to determine whether
similar un-stabilized hardware exists that can meet the TMT jitter requirements. Tests using representative TMT
tracking motions were then performed to measure jitter on similar existing hardware. The results of these hardware tests
have been analyzed. Test results, remaining risk assessment and further testing plans are presented.
The Gemini Observatory operates two telescopes, both in geographical areas that pose a significant risk of damage due
to earthquakes. To assess the potential of damage to telescope systems due to earthquake induced ground motion, a
system of accelerometers, data acquisition hardware and data analysis software is being installed at each telescope.
Information from these sensors will be used to evaluate the response at various locations on the telescope including the
primary and secondary mirror support structures, instruments, telescope mount, pier and adjacent ground. A detailed
discussion of the design of this sensor system is presented. Real time applications and potential future upgrades are also
discussed, including provisions for automatic subsystem parking and shutdown, laser shuttering, alarms and future
structural modifications designed to reduce the dynamic response of the telescope and its subsystems to earthquake
induced ground motion.
The Gemini Observatory is continuing in the preliminary design stages of upgrading the micro-controller and related data acquisition components for the Secondary Mirror Tip/tilt System (M2TS). The Gemini North M2TS has surpassed a decade of service in the scientific community, yet the designs at both sites are nearly twenty years old and maintenance costs continue to increase. The next generation M2TS acquisition system takes a look at today's more common practices such as alternatives to VME, and the use of Industry Pack modules and high-rate data logging. An overview of the refactored software design will be described including the use of The Real-Time Executive for Multiprocessor Systems, or RTEMS, as the operating system of choice to meet the real-time performance requirements.
The Gemini Observatory is currently in the early stages of a major upgrade of the Secondary Mirror Tip/tilt Systems
(M2TS). Although these systems continue to deliver good fast-steering and chopping performance at both sites, there are
persistent and occasionally time-consuming issues that need to be addressed in order for them to deliver their full
potential and further reduce downtime. We present an overview of the system, outline its capabilities, and review the
early commissioning process and some of the issues encountered. We describe the augmentation of the original system
with data logging features which made possible some critical servo tuning work that was key in delivering improved
performance. The hardware and software upgrade project to date is discussed, along with a brief overview of items it
intends to address.
The Gemini Secondary Mirror Tip/tilt Systems (M2TS) have greatly benefited from the availability of software-based
data logging-to-disk of internal variables at servo loop rates, enabling efficient testing and troubleshooting. Similar 'fast-logging-to-disk' systems are now being considered for other Gemini subsystems. We describe how this technique was
successfully applied to the M2TS, solving intractable tuning problems; a forward look will show how extensive and fully integrated logging and diagnostic capabilities are at the heart of the new design for the M2TS-2. Designers of new and
ever-larger and more complex telescope systems are challenged to consider the benefits of including such systems in
their own designs at an early stage - and to consider the costs in terms of ease of performing diagnostics and loss of
maintainability of not doing so.
The Gemini Observatory is in the final integration and test phase for its Multi-Conjugate Adaptive Optics (MCAO)
project at the Gemini South 8-meter telescope atop Cerro Pachón, Chile. This paper presents an overview and status of
the laser-side of the MCAO project in general and its Beam Transfer Optics (BTO), Laser Launch Telescope (LLT) and
Safety Systems in particular. We review the commonalities and differences between the Gemini North Laser Guide Star
(LGS) facility producing one LGS with a 10W-class laser, and its southern sibling producing five LGS with a 50W-class
laser. We also highlight the modifications brought to the initial Gemini South LGS facility design based on lessons
learned over 3 years of LGS operations in Hawaii. Finally, current integration and test results of the BTO and on-sky
LLT performance are presented. Laser first light is expected in early 2009.
The Gemini Multi-Conjugate Adaptive Optics project was launched in April 1999 to become the Gemini South
AO facility in Chile. The system includes 5 laser guide stars, 3 natural guide stars and 3 deformable mirrors optically
conjugated at 0, 4.5 and 9km to achieve near-uniform atmospheric compensation over a 1 arc minute square field of
Sub-contracted systems with vendors were started as early as October 2001 and were all delivered by July
2007, but for the 50W laser (due around September 2008). The in-house development began in January 2006, and is
expected to be completed by the end of 2008 to continue with integration and testing (I&T) on the telescope. The on-sky
commissioning phase is scheduled to start during the first half of 2009.
In this general overview, we will first describe the status of each subsystem with their major requirements, risk
areas and achieved performance. Next we will present our plan to complete the project by reviewing the remaining steps
through I&T and commissioning on the telescope, both during day-time and at night-time. Finally, we will summarize
some management activities like schedules, resources and conclude with some lessons learned.
The Acquisition and Guiding Unit of the Gemini Telescope is able to support two major signal-processing functions: off axis active optics correction, and off axis fast guiding and focus. Both functions are performed by using up to two different Shack-Hartmann wavefront sensors working in the visible (called the Peripheral Wavefront Sensors). In addition to these wavefront sensors, each facility instrument includes its On Instrument Wavefront Sensor, which provides on or off axis fast guiding, and in some cases focus and astigmatism correction. In this paper, we will describe the different wavefront sensors and the results obtained in closed loop in terms of image quality and temporal performance.
This paper describes the design and current status of the mount control system (MCS) for the Gemini telescopes. The MCS is responsible for the interface between the telescope computer system (TCS) and the hardware systems that are used to move the telescope's two main axes (azimuth and elevation). In order to do this, the MCS must process encoder signals and use these to close a position servo involving multiple motors. The MCS also provides several ancillary functions. These are: the servos for the main axis cable wraps, the servos for the telescopes counterbalance units, an interface to the safety interlock system and inputs for various sensors that will be placed around the telescope structure.