The EBEX Balloon-borne Experiment—Gondola, Attitude Control, and Control Software

Abstract

The E and B Experiment (EBEX) was a long-duration balloon-borne instrument designed to measure the polarization of the cosmic microwave background (CMB) radiation. EBEX was the first balloon-borne instrument to implement a kilopixel array of transition edge sensor (TES) bolometric detectors and the first CMB experiment to use the digital version of the frequency domain multiplexing system for readout of the TES array. The scan strategy relied on 40s peak-to-peak constant-velocity azimuthal scans. We discuss the unique demands on the design and operation of the payload that resulted from these new technologies and the scan strategy. We describe the solutions implemented, including the development of a power system designed to provide a total of at least 2.3kW, a cooling system to dissipate 590W consumed by the detectors' readout system, software to manage and handle the data of the kilopixel array, and specialized attitude reconstruction software. We present flight performance data showing faultless management of the TES array, adequate powering and cooling of the readout electronics, and constraint of attitude reconstruction errors such that the spurious B-modes they induced were less than 10% of the CMB B-mode power spectrum with r=0.05.

Modeling of stratospheric balloons and robust line-of-sight pointing control

“…However, in the literature, dynamical models of the balloon-borne system are rarely integrated in the control design. Instead, the control gains are generally tuned empirically based on ground testings [3,30,[35][36][37][38][39], with simple control structures such as Proportional-Integral-Derivative (PID) gains [18,32,33,[40][41][42] possibly with some dynamic filters [2,43,44]. To the authors knowledge, there exists no general model-based methodology for controller synthesis in the literature, and, more critically, experimental ground-based setups are not representative of the dynamics of the fully deployed system in flight (which cannot be obtained in laboratory due to the dimensions of the system), whereas flight experience proves that the lineof-sight control is essentially limited by the rejection of the natural pendulum-like modes of the flight chain [2], excited by wind disturbance.…”

Robust line-of-sight pointing control on-board a stratospheric balloon-borne platform

“…Once an accurate dynamical model is obtained, it is possible to address the pointing control of the optical instrument on-board the gondola, generally a telescope [3,5,[19][20][21] or siderostat [7,22,23]. Most often, simple control structures such as Proportional-Integral-Derivative (PID) gains are chosen [13,21,22,[24][25][26] and the control gains are tuned empirically based on ground testings [3,19,[27][28][29][30][31]. There exists no general model-based methodology for controller synthesis, and, more critically, experimental ground-based set-ups are not representative of the dynamics of the fully deployed system in flight, whereas flight experience proves that the line-of-sight control is essentially limited by the rejection of the natural modes of the flight chain excited by wind disturbances [2].…”