Spectra: one binary file per spectrum. Spectra can be processed using DOASIS or QDOAS software. Spectrum files are saved in folders numbered by date. Daily log files: for spectra (extra geometric information as well as latitude, longitude, solar zenith angle) and temperature (instrument, internal and external temperature measurements). Accelerometer: One ascii file per day with pitch, roll and yaw euler angles as the columns Images: taken by a small camera, co-directional with the MAX-DOAS, for context of broad light conditions (i.e. checking sunny/cloudy weather) Calibration files: Binary and text files for dark current, offset, slit function shape and wavelength calibrations

The current data set contains spectral atmospheric measurements from: - Multi-Angle Differential Optical Absorption Spectrometer (MAX-DOAS) - built in-house at NIWA Lauder by Dr Karin Kreher, Mr Paul Johnston and Mr Alan Thomas. Instrument description and setup details: MAX-DOAS Instrument Description: The MAX-DOAS instrument consists of a Czerny-Turner type ISA HR320 flat-field spectrograph with a focal length of 320 mm and an aperture ratio of F/4. The array detector is a Hamamatsu C7042 detector head with S7032-1007 sensor chip. The chip is back-thinned, allowing light to enter from the rear of the silicon substrate, which substantially increases the quantum efficiency over the whole spectral range, especially in the UV region (less than 400 nm). The sensitivity in the UV is important in order to obtain a good signal-to-noise ratio for BrO measurements. The detector signal is then passed to the computer via a 16-bit analogue to digital converter card. The detector is cooled to -20oC using a Peltier cooler to minimise the dark current noise caused by thermally excited electrons. The entrance optics consisted of an angled telescope mirror that reflects the measured light down through a focusing lens onto the entrance of a quartz fibre optic bundle leading into the spectrograph. The field of view of the telescope is ~0.5o. A webcam, also housed close to the entrance optics, records images of the sky in the spectrometer viewing direction at one minute intervals. These images are included in the dataset. Instrument Setup: The spectrometer was scanning wavelength regions in the UV-Vis region with a variable resolution spread over the pixel array CCD. Spectra were taken at multiple viewing angles (1,2,3,4,6,8,15,30,90o) in the open water and (-5,1,2,4,6,8,15,30,90o) in the ice (5th October - left ice) above the horizon. 90o is used as the reference viewing angle. Scattered sunlight was fed into the spectrometer using an optical fibre whose input was placed at the focal point of a lens receiving light from the rotating mirror which was setup to automatically adjust for the roll of the ship to maintain its viewing angle. The data is processed using 2 wavelength fitting regions as follows: M region: 323-348 nm in the UV retrieving: XS1=NO2 x 1e16, XS2=O3 x 1e19, XS6=O4x1e42, XS7=BrOx1e14, XS11 HCHOx1e16, XS12=slope O3 (to improve fit of O3 due to air mass changes with wavelength). And S region (visible) 416-443 nm, retrieving XS1=NO2 x 1e16, XS6=H2O x 1e22, XS7=O4x1e42, XS11=IOx1e14 The entrance optics of the tracker were cleaned daily using kimwipes. The dataset contains the following files: - FPS files, which are binary files generated by in-house software written by The National Institute of Water and Atmosphere (NIWA). - A MAX-DOAS log file, in text format - A MAX-DOAS error file, in text format - A configuration file, in text format