LISA LISA Three spacecrafts 2.5 10 9 m arms Laser Interferometry - - PowerPoint PPT Presentation

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LISA LISA Three spacecrafts 2.5 10 9 m arms Laser Interferometry - - PowerPoint PPT Presentation

Aug 10, 2023 107 likes •405 views

Ester Abram AN INTRODUCTION TO ITS POINTING DIFFICULTIES Master Student Supervisors: Ernst-Jan Buis (TNO) Niels van Bakel (Nikhef) LISA LISA Three spacecrafts 2.5 10 9 m arms Laser Interferometry No seismic noise

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SLIDE 1

LISA

Ester Abram Master Student Supervisors: Ernst-Jan Buis (TNO) Niels van Bakel (Nikhef) AN INTRODUCTION TO ITS POINTING DIFFICULTIES

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SLIDE 2

LISA

  • Three spacecrafts
  • ≈ 2.5 109 m arms
  • Laser Interferometry
  • No seismic noise

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SLIDE 3

Orbit

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SLIDE 4

Orbit

  • Equilateral triangle
  • Constant arm length
  • Tidal forces
  • Inclination

No “constant” triangle

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SLIDE 5

Pointing

  • Six laser links
  • Pointing
  • Tilt
  • Offset
  • FOV

How to?

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SLIDE 6

Content

  • Breathing angle
  • Point ahead angle
  • How to compensate
  • My work

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SLIDE 7

Breathing angle

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SLIDE 8

Breathing angle

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SLIDE 9

Breathing angle

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SLIDE 10

Breathing angle

Adjust telescopes

  • Optical Assembly Tracking

Mechanism (OATM)

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SLIDE 11

Breathing angle

Adjust telescopes

  • Optical Assembly Tracking

Mechanism (OATM)

  • Micronewton thrusters
  • Optical assembly

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SLIDE 12

Breathing angle

Adjust telescopes

  • Optical Assembly Tracking

Mechanism (OATM)

  • Micronewton thrusters
  • Optical assembly

Otherwise outside FOV (=8 𝜈𝑠𝑏𝑒)

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SLIDE 13

Six Laser Links

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SLIDE 14

Six Laser Links

  • Time delay

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SLIDE 15

Laser Link

Varying arm lengths and angles:

  • Signal
  • Pointing

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SLIDE 16

Laser Link

Varying arm lengths and angles:

  • Signal
  • Pointing

Point Ahead Angle (PAA) Otherwise you will ‘miss’

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SLIDE 17

Point Ahead Angle (PAA)

Due to relative velocity:

  • “Inplane” and

“Outplane” PAA

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SLIDE 18

Point Ahead Angle (PAA)

Due to relative velocity:

  • “Inplane” PAA
  • Telescope
  • “Outplane” PAA
  • PAAM

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SLIDE 19

PAA Outplane

  • Point ahead angle mechanism

(PAAM)

  • Two piezo stacks
  • Dynamic control
  • High precision

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SLIDE 20

PAA Outplane

  • Point ahead angle mechanism

(PAAM)

  • Two piezo stacks
  • Dynamic control
  • High precision

The PAAM will send the transmitted beam under an angle with the received beam

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SLIDE 21

PAA Inplane

Control telescopes:

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SLIDE 22

PAA Inplane

Control telescope:

  • It will receive the incoming

beam ‘straight’

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SLIDE 23

PAA Inplane

Control telescope:

  • It will receive the incoming

beam ‘straight’

  • Affects outgoing beam
  • Not dynamic control
  • Heavy (noise)

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SLIDE 24

My work

Find a/the best way to point

  • Different strategies:

‘Center’: Aim for the center

  • f the telescope

‘Wavefront’: Receive the incoming beam straight

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SLIDE 25

‘Center’ ‘Wavefront’

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SLIDE 26

‘Center’ ‘Wavefront’

Angle (rad) Angle (rad)

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SLIDE 27

My work

Find a/the best way to point

  • Different strategies:
  • ‘Center’
  • ‘Wavefront’
  • Different methods:
  • ‘No control’
  • ‘Full control’
  • ‘Step and stare’ (SS)

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SLIDE 28

My work - Goal

  • Good and fast simulation and calculations
  • Reliable
  • Optimized pointing
  • How to control the PAAM
  • How to control the telescope
  • Add additional inplane PAAM?

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SLIDE 29

Sources

  • http://www.astronomy.com/news/2018/11/looking-ahead-to-the-

lisa-gravitational-wave-detector

  • https://www.researchgate.net/figure/Realization-of-the-Point-Ahead-

Angle-Mechanism-The-mirror-is-glued-to-a- monolithical_fig4_321192271

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