Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Balloon-borne hard X-ray polarimetry with PoGOLite   PoGOLite is a hard X-ray polarimeter operating in the 25-100 keV energy band.
The instrument design is optimised for the observation of compact astrophysical
sources. Observations are conducted from a stabilised stratospheric balloon
platform at an altitude of approximately 40 km. The primary targets for first
balloon flights of a reduced effective area instrument are the Crab and
Cygnus-X1. The polarisation of incoming photons is determined using coincident
Compton scattering and photo-absorption events reconstructed in an array of
plastic scintillator detector cells surrounded by a bismuth germanate oxide
(BGO) side anticoincidence shield and a polyethylene neutron shield. A custom
attitude control system keeps the polarimeter field-of-view aligned to targets
of interest, compensating for sidereal motion and perturbations such as
torsional forces in the balloon rigging. An overview of the PoGOLite project is
presented and the outcome of the ill-fated maiden balloon flight is discussed.

31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom