Validation of novel pointing concepts for LISA

verfasst von: N. F. Hasselmann
betreut von: Gerhard Heinzel
Abstract: Detecting low-frequency gravitational waves using ground-based interferometric detectors is impossible today and in the near future due to seismic activity. Space-based gravitational wave detectors are not limited by this noise source and permit much longer arm-lengths. However, going to space also comes with challenges: Orbital dynamics result in ŕuctuations of the apex angles of the near equilateral formation consisting of three satellites containing test masses, between which the distance ŕuctuations are measured to detect gravitational waves. A line-of-sight pointing is thus required to continuously detect gravitational waves with minimal excess noise. Without active pointing, the interferometric contrast would degrade (after only roughly 1 ks), and the signal would őnally be lost entirely. Within the frame of this work, aspects of two advanced pointing concepts, In- Field and Siderostat Pointing, will be investigated experimentally to show their feasibility. These concepts are based on őxed telescope modules and one to two actuated mirrors per spacecraft, yielding many beneőts while presenting some unique challenges (e.g., reduced self-gravity efects and no need for a ŕexible harness vs. additional projection efects). In doing so, alternatives for the baseline pointing concept dubbed ’Telescope pointing’ are pointed out. In Telescope pointing, one to two telescopes, including their gravitational reference sensors and optical benches, are actuated during active pointing per spacecraft. This concept’s angular noise performance has yet to be shown, which is an especially challenging feat on-ground under representative conditions due to the large actuated masses and the cable harness connecting moving parts to the satellite. The investigations presented herein typically employ ultra-precise optical metrology, namely heterodyne interferometry, to measure optical pathlengths and angles. This allows probing key performance parameters and testing functionalities (such as coupling of angle to pathlength, angular stability, and compensation of coupling of angular to pathlength noise). The studies őnd that the alternative payload architectures are, in principle, realizable and demonstrate critical core functions such as active pointing. Additionally, possible improvements in the design of not only those but all pointing schemes are detailed.
Organisationseinheit(en): QUEST Leibniz Forschungsschule
Typ: Dissertation
Anzahl der Seiten: 145
Publikationsdatum: 05.03.2025
Publikationsstatus: Veröffentlicht
Elektronische Version(en): https://doi.org/10.15488/18641 (Zugang: Offen)
: Details im Forschungsportal „Research@Leibniz University“

BibTeX

@phdthesis{de2db5ff9f8e455586df542fefb95fb4,
title = "Validation of novel pointing concepts for LISA",
abstract = "Detecting low-frequency gravitational waves using ground-based interferometric detectors is impossible today and in the near future due to seismic activity. Space-based gravitational wave detectors are not limited by this noise source and permit much longer arm-lengths. However, going to space also comes with challenges: Orbital dynamics result in {\'r}uctuations of the apex angles of the near equilateral formation consisting of three satellites containing test masses, between which the distance {\'r}uctuations are measured to detect gravitational waves. A line-of-sight pointing is thus required to continuously detect gravitational waves with minimal excess noise. Without active pointing, the interferometric contrast would degrade (after only roughly 1 ks), and the signal would {\H o}nally be lost entirely. Within the frame of this work, aspects of two advanced pointing concepts, In- Field and Siderostat Pointing, will be investigated experimentally to show their feasibility. These concepts are based on {\H o}xed telescope modules and one to two actuated mirrors per spacecraft, yielding many bene{\H o}ts while presenting some unique challenges (e.g., reduced self-gravity efects and no need for a {\'r}exible harness vs. additional projection efects). In doing so, alternatives for the baseline pointing concept dubbed {\textquoteright}Telescope pointing{\textquoteright} are pointed out. In Telescope pointing, one to two telescopes, including their gravitational reference sensors and optical benches, are actuated during active pointing per spacecraft. This concept{\textquoteright}s angular noise performance has yet to be shown, which is an especially challenging feat on-ground under representative conditions due to the large actuated masses and the cable harness connecting moving parts to the satellite. The investigations presented herein typically employ ultra-precise optical metrology, namely heterodyne interferometry, to measure optical pathlengths and angles. This allows probing key performance parameters and testing functionalities (such as coupling of angle to pathlength, angular stability, and compensation of coupling of angular to pathlength noise). The studies {\H o}nd that the alternative payload architectures are, in principle, realizable and demonstrate critical core functions such as active pointing. Additionally, possible improvements in the design of not only those but all pointing schemes are detailed.",
author = "Hasselmann, {N. F.}",
year = "2025",
month = mar,
day = "5",
doi = "10.15488/18641",
language = "English",
publisher = "Leibniz Universit{\"a}t Hannover",
school = "Leibniz University Hannover",
}