Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Differential optical shadow sensor for sub-nanometer displacement
  measurement and its application to drag-free satellites   We present a method for 3D sub-nanometer displacement measurement using a set
of differential optical shadow sensor. It is based on using pairs of collimated
beams on opposite sides of an object that are partially blocked by it. Applied
to a sphere, our 3-axis sensor module consists of 8 parallel beam-detector sets
for redundancy. The sphere blocks half of each beam power in the nominal
centered position, and any displacement can be measured by the differential
optical power changes amongst the pairs of detectors. We have experimentally
demonstrated a displacement sensitivity of 0.87 nm/rtHz at 1 Hz and 0.39
nm/rtHz at 10 Hz. We describe the application of the module to the inertial
sensors of a drag-free satellite, which can potentially be used for navigation,
geodesy and fundamental science experiments as well as ground based
applications.

27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc