Space Interferometry Mission

2000 ◽  
Author(s):  
Stephen C. Unwin ◽  
Michael Shao
Keyword(s):  
Space Interferometry

Investigation on a Flexible Tether Slackness Based on In- and Out-of Plane Libration Angles

2012 ◽  
Vol 225 ◽  
pp. 411-416 ◽  
Author(s):  
Aaron Aw Teik Hong ◽  
Renuganth Varatharajoo
Keyword(s):  
Equation Of Motion ◽  
Rigid Bodies ◽  
Attitude Dynamics ◽  
Orbit Transfer ◽  
Operation System ◽  
Satellite Systems ◽  
Out Of Plane ◽  
Tethered Satellite Systems ◽  
Libration Angle ◽  
Space Interferometry

Tethered Satellite Systems (TSS) have been used in various applications such as in performing space interferometry, orbit transfer and other relevant fields. As far as the operation system of a TSS is concerned, it is crucial to ensure that the tether will not go slack as its slackness would adversely affects the overall operation outcome due to an undesirable system dynamics. Therefore, it is important to investigate the types of conditions that will cause the tether slackness. Investigations on in-plane and out-of plane libration angles can be utilized to measure at what point that the tether will go slack. Based on previous research works, usually a rigid tether comprising of a uniformed mass is considered while the connecting two satellites are regarded as point masses in order to simplify the governing dynamics equation of motion. However, in order to develop a much more accurate modeling, a flexible tether is chosen by further incorporating the reeling mechanism, attitude dynamics of rigid bodies and tether deformations. Furthermore, a tether has a tendency to go slack if the in-plane and out-of plane libration angle exceeds 65° and 60° respectively regardless of the types of tether utilized whether it being a rigid or a flexible one. Thus, the tension of the tether will serves as a constraint and plotted against the in-plane and out-of plane libration motions that would be attained via the generalized forces. The results will then be analyzed to establish in-plane and out-of plane libration boundaries. Subsequently, the in-plane and out-of plane operation contrains are established for TSS corresponding to a reference mission.

Average phase calculations with near-field diffraction algorithms for the Space Interferometry Mission

2000 ◽  
Author(s):  
Miltiadis V. Papalexandris ◽  
Scott A. Basinger ◽  
David C. Redding
Keyword(s):  
Near Field ◽  
Space Interferometry

scholarly journals Quasar Astrophysics with the Space Interferometry Mission

2002 ◽  
Vol 19 (1) ◽  
pp. 5-9 ◽  
Author(s):  
S. C. Unwin ◽  
A. E. Wehrle ◽  
D. L. Jones ◽  
D. L. Meier ◽  
B. G. Piner
Keyword(s):  
Accretion Disk ◽  
Optical Emission ◽  
Galaxy Mergers ◽  
Proper Motions ◽  
Optical Interferometer ◽  
Photometric Variability ◽  
Relativistic Jet ◽  
Precision Astrometry ◽  
Insight Into ◽  
Space Interferometry

AbstractPrecision optical astrometry of quasars and active galaxies can provide important insight into the spatial distribution and variability of emission in compact nuclei. SIM — the Space Interferometry Mission — will be the first optical interferometer capable of precision astrometry on quasars. Although it is not expected to resolve the emission, it will be very sensitive to astrometric shifts, for objects as faint as R magnitude 20. In its wide-angle mode, SIM will yield 4 microarcsecond absolute positions, and proper motions to about 2 microarcsecond/yr. A variety of AGN phenomena are expected to be visible to SIM on these scales, including time and spectral dependence in position offsets between accretion disk and jet emission. SIM should be able to answer the following questions. Does the most compact optical emission from an AGN come from an accretion disk or from a relativistic jet? Do the relative positions of the radio core and optical photocentre of quasars used for the reference frame tie change on the timescales of their photometric variability? Do the cores of galaxies harbour binary supermassive black holes remaining from galaxy mergers? In this paper we briefly describe the operation of SIM and the quasar measurements it will make. We estimate the size of the astrometric signatures which may be expected, and we discuss prospects for using astrometry as a fundamental tool for understanding quasar nuclei.

Sign in / Sign up

Export Citation Format

Share Document