LCOGT are currently building and deploying a worldwide network of at least fifteen 1-meter
and twenty-four 0.4-meter telescopes to three sites in each hemisphere, enabling
extended, redundant and optimally continuous coverage of time variable or transient
sources. Each site will support two or more 1m telescopes and four or more 0.4m
All telescope classes provide a full range of optical narrow-band and broad-band UBVRI
and ugriZY imaging filters. All telescopes are being equipped with a moving light-bar flatfielding
system called Lambert.
The 1m network is intended primarily for science observing while the 0.4m network
additionally provides educational opportunities to participating schools and institutes. The
global network is designed to accommodate multiple science, educational and rapid
For LCOGT, the network IS the telescope.
Scientific performance specifications, a necessity for ease of commissioning and minimal maintenance, and a desire for
automated sensing and remote collimation have led to novel designs and features in LCOGT's one-meter Optical Tube
Assembly (OTA). We discuss the design and performance of the quasi-RC optical system with 18 point whiffletree and
radial hub mount. Position probes and IR temperature sensors on the primary and secondary mirrors give feedback for
active collimation and thermal control. A carbon fiber/epoxy composite truss, with unique spherical node connections,
mounts to parallel and offset Invar vanes. A flexure based, closed loop, 3-DOF secondary mirror mechanism is used for
tip/tilt collimation. The optics and deflections of the OTA components were iteratively designed for passive collimation
with a changing gravity vector. We present the FEA predictions, measured deflections, and measured hysteresis for
many of the components. Vibration modes, amplitudes, and damping of the system are presented with an FFT frequency
analysis. Thermal CTE effects on loading and focal position are quantified. All of these system effects are then related to
the overall scientific performance of the 1.0 m telescope.
Traditional dome flat fielding methods typically have difficulties providing spatially uniform illumination and adequate
flux over a telescopic instrument's entire spectral range. Traditional flat fielding screens, with an illumination source at
least the size of the primary, can be difficult or impractical to mount and uniformly illuminate. The Las Cumbres
Observatory Global Telescope Network (LCOGTN) will consist of approximately 50 robotic telescopes of 0.4 m, 1.0 m,
and 2.0 m apertures with instrument bandwidth ranging from 350 - 1800 nm. The network requires a robust flat-field
solution to fit in compact enclosures.
A scanning illuminated flat fielding bar, Lambert, was developed to meet these requirements. Illumination is from a
linear arrangement of sources that are spatially dispersed by a narrow holographic or glass diffuser equal in length to the
primary's diameter. We have investigated a linearly scanning, enclosure mounted, deployable unit, and a rotary scanning,
telescope mounted unit. For complete visible-light bandwidth, a set of different color LEDs is used. The source density,
scan speed, and variable intensity tunes the flux to the instrument wavelength and bandwidth. The Lambert flat fields in
comparison to sky flats match pixel to pixel variations better than 0.5%; large scale illumination differences, which are
stable and repeatable, are ~1%.