Pre-Phase A Report - Lisa - Nasa

Recommendations

Info

164 Chapter 8 Technology Demonstration in Space the location of one proof mass, then the jitter of 10−8 rad/ √ Hz corresponds to a displacement of 2×10−9 m/ √ Hz at the location of the other proof mass. This is within the allowable limit of item 2, so condition (i) on attitude is more restrictive than condition (ii), etc. 4. In order to achieve the target strain sensitivity across the armlength of 5×106 km, the interferometer displacement noise must be lower than approximately 10 −11 m/ √ Hz across the MBW. This includes all optical effects, as well as spurious proof-mass motions. Allowing for reasonable apportioning of errors across the various contributions, the requirement on the optics alone becomes over the MBW. 8.2 ELITE Mission profile 10 −12 m/ √ Hz 8.2.1 Orbit and disturbance environment Baseline option. For the baseline GEO option (and for a shared launch into higher orbits), the main disturbance will be radiation pressure with a nominal force magnitude of ≈ 10 µN (solar pressure 4.644×10 −6 N/m 2 ; Earth albedo plus IR pressure ≈ 0.2 of solar pressure), modulated at the orbit frequency due to the variation in the direction of the line-of-sight to the Sun. This disturbance will be essentially uniform, with only slight stochastic variations due to solar fluctuations amounting to a few percent of the nominal values. The largest stochastic disturbance is likely to be noise in the thrusters which may be on the order of 1 µN (rms across the MBW). De-scoped option. For the de-scoped option which may be necessary due to cost, the most accessible orbit would be GTO (Geostationary Transfer Orbit). For example, from a nominal Ariane 5 launch into GTO, the resulting orbit will be low-inclination, highly eccentric, with a perigee altitude of ≈ 600 km (velocity ≈ 9.9 km/s), an apogee altitude of 35786 km (velocity ≈ 1.6 km/s), and an orbit period of ≈ 10.6 hours. In the vicinity of perigee, aerodynamic drag will dominate, with a nominal magnitude of ≈ 0.1mN opposite the direction of travel (atmospheric density ≈ 5×10 −13 kg/m 3 at 600 km, solar maximum; drag coefficient ≈ 2.2, spacecraft projected surface area ≈ 1m 2 ). For most of the orbit, the altitude will exceed 1000 km, and the aerodynamic drag will be negligible compared with radiation pressure (≈ 10 µN). The comparitively large drag at perigee will saturate the electric thrusters and the inertial sensors, requiring an undesirable switching of electrostatic suspension forces and a corresponding reset and calibration every orbit. It would thus be desirable to boost the orbit perigee to above 1000 km in order to overcome this problem. Furthermore, the GTO trajectory traverses the trapped radiation belts twice per orbit, leading to an integrated electric charge build-up on each proof mass of about 10 −10 C per orbit. However, ground tests have shown that this high charge rate can be managed by enhancing the performance of the discharge system. 3-3-1999 9:33 Corrected version 2.08
8.3 ELITE Technologies 165 8.2.2 Coarse attitude control It is necessary to perform a continuous slewing motion in order to keep the solar array pointed at the Sun to within ≈ 1 deg. This will require a continuously-varying angular acceleration with a peak value of ≈ 10−7 rad/s2 which corresponds to a torque of ≈ 10−5 Nm for nominal spacecraft dimensions. This torque could be supplied by the ion thrusters [TBD]. However, a cold-gas attitude control system will also be required for safemodes and for the spin-up/down procedure required for stabilising the satellite during the apogee boost (if a solid apogee boost motor is used to minimise the costs in the baseline option). The nominal mission lifetime is six months. This is sufficient for testing the performance of the accelerometers, lasers, interferometer, and thrusters, and for partially assessing their longevity and reliability in the space environment. The mission could be extended at the expense of higher operations costs. 8.3 ELITE Technologies 8.3.1 Capacitive sensor The capacitive sensors must be designed to meet the appropriate requirements on proofmass isolation and readout (for control) along all three translational axes. The three attitude degrees-of-freedom of each proof mass must also be measurable and controllable. Existing spaceborne accelerometer technology falls short of the LISA requirements by many orders of magnitude. It is necessary to develop the sensor technology dedicated to LISA’s requirements. The aim is to test this sensor on ELITE. 8.3.2 Laser interferometer Current ground-based laser interferometry more than meets the requirements of ELITE (and LISA), but only in a much higher frequency regime (kHz instead of mHz). It is necessary to demonstrate the technology required for low-frequency operation, and to test the functionality in the space environment. 8.3.3 Ion thrusters The main requirements for the ELITE thrust system is to provide sufficient steady-state thrust to offset the external disturbance forces and to provide the six-degree-of-freedom drag-free/attitude control. Existing field-effect ion thrusters operating in the micro- Newton regime are the most suitable technology but have to be further developed for LISA. It is known that the thruster noise characteristics play a key role in the noise budget for LISA so the thrusters must be developed and flight-tested with these considerations in mind. Corrected version 2.08 3-3-1999 9:33
Page 1 and 2:
LISA Laser Interferometer Space Ant
Page 3 and 4:
LISA Laser Interferometer Space Ant
Page 5 and 6:
Foreword The first mission concept
Page 7 and 8:
The result of the Team-X study was
Page 9 and 10:
Contents Foreword iii Executive Sum
Page 11 and 12:
Contents ix 4.2.3 Acceleration nois
Page 13 and 14:
Contents xi 9 Science and Mission O
Page 15 and 16:
Executive Summary 1 Executive Summa
Page 17 and 18:
Executive Summary 3 Complementarity
Page 19 and 20:
Mission Summary 5 LISA Mission Summ
Page 21 and 22:
Chapter 1 Scientific Objectives By
Page 23 and 24:
1.1 Theory of gravitational radiati
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
1.2 Low-frequency sources of gravit
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Chapter 2 Different Ways of Detecti
Page 53 and 54:
2.2 Ground-based detectors 39 2.2 G
Page 55 and 56:
2.2 Ground-based detectors 41 Count
Page 57 and 58:
2.4 Spacecraft tracking 43 2.4 Spac
Page 59 and 60:
2.7 Heliocentric versus geocentric
Page 61 and 62:
2.8 The LISA concept 47 telescopes
Page 63 and 64:
2.8 The LISA concept 49 Figure 2.6
Page 65 and 66:
2.8 The LISA concept 51 seem rather
Page 67 and 68:
Chapter 3 Experiment Description 3.
Page 69 and 70:
3.1 The interferometer 55 Fiber to
Page 71 and 72:
3.1 The interferometer 57 3.1.4 Sys
Page 73 and 74:
3.1 The interferometer 59 Figure 3.
Page 75 and 76:
3.1 The interferometer 61 3.1.6 Las
Page 77 and 78:
3.1 The interferometer 63 signal sh
Page 79 and 80:
3.1 The interferometer 65 for a sin
Page 81 and 82:
3.2 The inertial sensor 67 design (
Page 83 and 84:
3.2 The inertial sensor 69 and the
Page 85 and 86:
3.2 The inertial sensor 71 Figure 3
Page 87 and 88:
3.2 The inertial sensor 73 sufficie
Page 89 and 90:
3.3 Drag-free/attitude control syst
Page 91 and 92:
3.3 Drag-free/attitude control syst
Page 93 and 94:
Chapter 4 Measurement Sensitivity 4
Page 95 and 96:
4.1 Sensitivity 81 averaged transfe
Page 97 and 98:
4.2 Noises and error sources 83 The
Page 99 and 100:
4.2 Noises and error sources 85 Tab
Page 101 and 102:
4.2 Noises and error sources 87 cod
Page 103 and 104:
4.2 Noises and error sources 89 cha
Page 105 and 106:
4.2 Noises and error sources 91 fre
Page 107 and 108:
4.2 Noises and error sources 93 ele
Page 109 and 110:
4.2 Noises and error sources 95 is
Page 111 and 112:
4.2 Noises and error sources 97 and
Page 113 and 114:
4.2 Noises and error sources 99 Eq.
Page 115 and 116:
4.3 Signal extraction 101 here that
Page 117 and 118:
4.3 Signal extraction 103 phase loc
Page 119 and 120:
4.4 Data analysis 105 • LISA obse
Page 121 and 122:
4.4 Data analysis 107 for ground-ba
Page 123 and 124:
4.4 Data analysis 109 that are defi
Page 125 and 126:
4.4 Data analysis 111 with the phas
Page 127 and 128: 4.4 Data analysis 113 density Sn(f)
Page 129 and 130: 4.4 Data analysis 115 box (in stera
Page 131 and 132: 4.4 Data analysis 117 LISA’s dist
Page 133 and 134: Chapter 5 Payload Design 5.1 Payloa
Page 135 and 136: 5.2 Payload structural components 1
Page 137 and 138: 5.2 Payload structural components 1
Page 139 and 140: 5.4 Mass estimates 125 5.4 Mass est
Page 141 and 142: 5.7 Thermal analysis 127 the Y-shap
Page 143 and 144: 5.8 Telescope assembly 129 surface
Page 145 and 146: 5.9 Payload processor and data inte
Page 147 and 148: 5.9 Payload processor and data inte
Page 149 and 150: Chapter 6 Mission Analysis 6.1 Orbi
Page 151 and 152: 6.3 Injection into final orbits 137
Page 153 and 154: 6.4 Orbit configuration stability 1
Page 155 and 156: 6.5 Orbit determination and trackin
Page 157 and 158: Chapter 7 Spacecraft Design 7.1 Sys
Page 159 and 160: 7.1 System configuration 145 2220 m
Page 161 and 162: 7.1 System configuration 147 7.1.4
Page 163 and 164: 7.2 Spacecraft subsystem design 149
Page 165 and 166: 7.3 Micronewton ion thrusters 151 b
Page 167 and 168: 7.3 Micronewton ion thrusters 153 F
Page 169 and 170: 7.3 Micronewton ion thrusters 155 (
Page 171 and 172: 7.3 Micronewton ion thrusters 157 F
Page 173 and 174: 7.4 Mass and power budgets 159 The
Page 175 and 176: Chapter 8 Technology Demonstration
Page 177: 8.1 ELITE - European LISA Technolog
Page 181 and 182: 8.4 ELITE Satellite design 167 inco
Page 183 and 184: Chapter 9 Science and Mission Opera
Page 185 and 186: 9.2 Mission operations 171 9.2 Miss
Page 187 and 188: 9.3 Operating modes 173 Power savin
Page 189 and 190: Chapter 10 International Collaborat
Page 191 and 192: 10.3 Schedule 177 The ESA Project M
Page 193 and 194: References [1] C.W. Misner, K.S. Th
Page 195 and 196: References 181 [35] C. Cutler, T.A.
Page 197 and 198: References 183 [77] J.E. Faller and
Page 199 and 200: References 185 [104] E. Grun, H.A.
Page 201 and 202: List of Acronyms - and other abbrev
Page 203 and 204: List of Acronyms 189 LHC Large Hadr
Page 205: Rear cover figure : This Report has
show all

Pre-Phase A Report - Lisa - Nasa

Create successful ePaper yourself

Delete template?

Save as template?