Tiny torsion-type gravitational wave detector in space: SWIM

Wataru Kokuyama(University of Tokyo)

on behalf of SWIM team

SWIM: Technology Demonstration Module

80mm

Sensor Module

Test Mass

50mm

- Torsion-type GW detector with noncontact-controlled test mass- A tiny module on a piggyback satellite

- Position sensing with reflective infrared sensors- Actuation with coil-magnet pairs- Digital PID control implemented on FPGA- Space-qualified computer (SpC2) along with this box

120x180x220 mm3, 3.5kg

Demonstrate important technologies for DPF(FPGA-based feedback control, SpC2, etc.)

SpC2

Photo of SDS-1 and other piggy-back satellitesSDS-1 (equipped with SWIM) ©JAXA

Not a CG!Jan. 23, 2009

Launch of SWIM

SWIM Operation- Operation time : Only 2-5 days/month!

- # of Paths: 39- Downloaded data: ~ 16.4MB

Path: a comm. session with the satellite (~10min.)

Statistics as of May 2010

- Successful test mass control (Total ~ 7 hours)- Noise spectrum of the sensor- Interesting behavior of test mass- Clock synchronization with GPS (6-digits accuracy)- In preparation for demonstration of GW observation

Initial Check-out

Lock Acquisition

CalibrationNoise

Measurement

(~Apr. 2009)(~May. 2009)

Net power-on time : 46.7 hours in 16 months

(~Mar. 2010) (~Mar. 2010)

- send commands to the detector- typically 1 path/day

SWIM Results: Lock Acquisition

Vertical Control Start

Horizontal Control Start

SWIMResults: Noise Level

Spin stabilized(Dec. 2009)

3-Axis, earth-oriented(Jan. 2010)

3-Axis, solar-oriented(Jan. 2010)

Coupling with satellite spin (~50mHz)

SWIMResults: Test mass as a Foucault pendulumJust after lock acquisition, test mass’s horizontal oscillation was observed.

Center of mass motion

0.2mmEstimated spin rate ： 46.7 mHzMeasured by Gyro ： 46.3 mHz

in satellite-fixed coordinate~2Hz

~50 mHz

~2Hz

a Foucault pendulum on the spinning satellite

SDS-1

Observation Plan with SWIM

Tokyo

SWIM

Observation & data analysis demonstrations are planned.

2) Coincident observation with ground-based torsion-bar antenna at U.Tokyo / Kyoto U.

- Detector in low-earth orbitmoves around the earth in every 100min.

http://www.astro.ucla.edu/~ghezgroup/gc/journey/images/mw7b_gleason.jpg

1) GWs from the Galactic Center

- Main target for DPF observations - SWIM can be oriented at GC.

Galactic center10-digits worse sensitivity than DPF…

Interesting analysis?(If there is, it can be applied to DPF.)