The next generation of space telescopes will be designed to meet increasingly challenging science goals. The operating
environment and required precision of these telescopes will make complete verification via ground tests impossible, and
will place a greater reliance on numerical simulation. The current state of the art in thermal, mechanical and optical
modeling involves three disparate computational models, several analysis codes and tools to transition results between
these models. However, the active controls necessary to meet the next generation of requirements for space telescopes
will require integrated thermal, structural, optical and controls analysis. To meet these challenges, JPL has developed
Cielo, an in-house finite element tool capable of multi-physics simulations using a common finite element model, for
thermal, structural and optical aberration analysis. In this paper, we will discuss the use of Cielo for analysis of a
coronagraph and an occulter designed to observe Earth-like planets around nearby stars. We will compare thermal and
structural results from Cielo with results from commercial off the shelf (COTS) tools to verify the new approach. We
will perform variations of key parameters to demonstrate how margins and uncertainties can be quantified using the new
approach.
KEYWORDS: Mirrors, Actuators, Sensors, Temperature sensors, Temperature metrology, Space telescopes, Wavefront sensors, Algorithm development, Lightweight mirrors, Finite element methods
The next generation of space telescopes will be required to meet very challenging science goals. In order to
achieve these goals, the size of the primary mirror will need to be increased. However, since current
telescopes are reaching their limits in terms of size and mass, new designs will require advanced
technologies such as lightweight mirrors and active optical control. Traditional shape control of the primary
mirror relies on feedback from a wavefront sensor located in the optical path. However, a wavefront sensor
reduces the amount of light available for image formation. Therefore, to view very dim objects, it will be
necessary to use a different type of sensor. In this work, a quasi-static shape control algorithm is developed
to correct errors in the mirror due to thermal disturbances using only sensors embedded in the mirror.
Control algorithms are presented for both embedded strain gages and temperature sensors. Finite element
models of both a simple flat plate mirror and a rib-stiffened mirror are generated and analyzed using
Nastran. The flat plate model, with surface-parallel actuation is used to compare the two algorithms.
Following this, the parametric model for a rib-stiffened mirror is used to analyze the effects of the shape
control algorithm as the mirror geometry is changed. It is shown that correction of a mirror can be
achieved using these embedded sensors.
KEYWORDS: Mirrors, Space telescopes, Optical instrument design, Systems modeling, Lightweight mirrors, Actuators, Performance modeling, Finite element methods, Space mirrors, Space operations
Development of low-cost, lightweight space imaging systems requires a combination of technologies including
lightweight optics to reduce the areal density of the mirrors and application of controls-structures technologies to
compensate for the increased flexibility of these systems. These new design technologies have led to many new
possibilities for architectures of large space telescopes, creating a necessity for new design tools during the conceptual
design phase. The MIT Space Systems Laboratory (MIT-SSL) is examining alternative architectures for a Modular
Optical Space Telescope (MOST) by developing a tool to automatically generate unique realizations of a spacecraft
based upon parametric inputs to the model. This tool allows system metrics to be evaluated across combinations of
design variables so that promising architecture families utilizing different technologies can be identified on the basis of
system performance. This paper will describe advances to the structural components of the MOST model, particularly
the primary mirror and secondary support tower. Lightweight, rib-stiffened mirrors and a variety of geometries for a
lightweight secondary support tower have been modeled. Both of these parameterized sub-components can be analyzed
to determine the effects of changing geometries on the structural stiffness. These advanced components can then be
used in the system in order to more fully understand the effects of lightweight structures on the system performance
metrics.
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