Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A compact, robust, and transportable ultra-stable laser with a
  fractional frequency instability of $1\times10^{-15}$   We present a compact and robust transportable ultra-stable laser system with
minimum fractional frequency instability of $1\times10^{-15}$ at integration
times between 1 to 10 s. The system was conceived as a prototype of a subsystem
of a microwave-optical local oscillator to be used on the satellite mission
STE-QUEST (Space-Time Explorer and QUantum Equivalence Principle Space Test,
http://sci.esa.int/ste-quest/). It was therefore designed to be compact, to
sustain accelerations occurring during rocket launch, to exhibit low vibration
sensitivity, and to reach a low frequency instability. Overall dimensions of
the optical system are $40\textrm{ cm}\times20\textrm{ cm}\times30\textrm{
cm}$. The acceleration sensitivities of the optical frequency in the three
directions were measured to be $1.7\times10^{-11}/g$, $8.0\times10^{-11}/g$,
and $3.9\times10^{-10}/g$, and the absolute frequency instability was
determined via a three-cornered hat measurement. The design is also appropriate
and useful for terrestrial applications.

32
The categories of this paper are: atom-ph
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph