  We report the detection of a thick disk in the edge-on, low surface
brightness (LSB), late-type spiral ESO 342-G017, based on ultra-deep images in
the V and R bands obtained with the VLT Test Camera during Science Verification
on UT1. All steps in the reduction procedure are fully described, which,
together with an extensive analysis of systematic and statistic uncertainties,
has resulted in surface brightness photometry that is reliable for the
detection of faint extended structure to a level of V = 27.5 and R = 28.5
mag/square arcsec. The faint light apparent in these deep images is
well-modeled by a thick exponential disk with an intrinsic scale height about
2.5 times that of the thin disk, and a comparable or somewhat larger scale
length. Deprojection including the effects of inclination and convolution with
the PSF allow us to estimate that the thick disk contributes 20-40% of the
total (old) stellar disk luminosity of ESO 342-G017. To our knowledge, this is
the first detection of a thick disk in an LSB galaxy, which are generally
thought to be rather unevolved compared to higher surface brightness galaxies.
