LISA Mission Description

    This table summarises the basic mission elements and characteristics of LISA.

    Science Objectives
    Study the formation and evolution of compact binary stars in the Milky Way Galaxy
    Trace the origin, growth and merger history of massive black holes across cosmic ages
    Probe the dynamics of dense nuclear clusters using extreme mass-ratio inspirals (EMRIs)
    Understand the astrophysics of stellar origin black holes
    Explore the fundamental nature of gravity and black holes
    Probe the rate of expansion of the Universe
    Understand stochastic gravitational wave backgrounds and their implications for the early Universe and TeV-scale particle physics
    Search for GW bursts and unforeseen sources

    Event rates
    Frequency band 1 × 10−4 Hz to 1 Hz, (2 × 10−5 Hz to 1 Hz as a goal)
    Massive black hole mergers 1 yr−1 to 1000 yr−1
    Extreme mass ratio insiprals 1 yr−1 to 100 yr−1
    Galactic Binaries ∼25 000 resolvable out of a total of ∼30 × 106 in the LISA band

    Mission
    Duration 4 years science orbit, (∼ 6.5 years including transfer and commissioning)
    Orbits Three drag-free satellites in heliocentric orbits, semimajor axis approx. 1 AU, eccentricty e ≈ 0.0096, inclination ı ≈ 0.96°
    Spacecraft bus Provides power, communication, and attitude and orbit control (AOCS) on science orbit. Micronewton propulsion system, magnetically and gravitationally controlled design
    AOCS Derived from test mass position and received laser, star tracker as backup
    Pointing Spacecraft attitude jitter < 10 nrad/√Hz
    Mass Mass (spacecraft incl. payload): 1898 kg
    Power Science mode: 1.6 kW
    Constellation Equilateral triangle, 2.5 × 106 km armlength, trailing Earth by ~20°, inclined by 60° with respect to the ecliptic. Armlength variation < 1 %, angular variaton ±0.8°, relative velocity between spacecraft < 20 m/s
    Communications Data generation rate 17 kbps per spacecraft, downlink via X-band, downlink data rate 150 kbps during 8 hours contact.
    Contact schedule One 8 hour pass per day to one spacecraft. Data of other two s/c transferred to master via laser link
    Total mass Including margin, launch adapter and propellant: 6642 kg
    Launcher Ariane 6.4
    Launch date 2034

    Payload
    Laser 2 per spacecraft, 2 W ouput power at end-of-life, wavelength 1064 nm, frequency stability (pre-stabilised) 300 Hz/√Hz, fractional power stability 10−3/√Hz
    Optical bench 2 per spacecraft, material with low thermal expansion (Zerodur), monolithic construction (hydroxy-catalysis bonding)
    Inteferometry heterodyne interferometry, 10 pm/√Hz requirement. Inter-spacecraft ranging to ∼1 m, clock tone transfer
    Gravitational reference sensor 46 mm × 46 mm × 46 mm test mass made from AuPt alloy (73:27), electrostatically controlled, optical readout, residual acceleration <3 × 10−15 m/s2/√Hz (10−9 m/s2 at DC)
    Telescope 2 per spacecraft, 30 cm off-axis telescope. Changing inter-spacecraft angle compensated by telescope movement.
    Mass Net mass per payload: 475 kg
    May 2018