SPIRALE is a spectrometer with six tunable diode lasers dedicated to in situ measurements of trace compounds in the upper troposphere and the stratosphere up to 35 km altitude.
The 6 laser beams circulate in a multipass HERRIOTT cell located below the gondola. The lower mirror of the two-mirror cell is fixed at the top of a deployable mast. The distance between mirror is about 3.50 m. Given the curvature of the two identical mirrors, two stable optical configuration can be used : first 86 reflections and 300 m optical path, second 156 reflections and 554 m optical path, by moving the lower mirror 5 mm up.
The mast is deployed during the flight to have the first measurements at the tropopause. Around the instrument, a rigid metal frame encompasses it, in order to have a instrument-safe landing.
Inside the instrument, three liquid nitrogen cryostats, hold the six diode lasers and the 12 detectors.
Vertical profiles of concentrations of a great number of species like O3, CH4, CO, CO2, N2O, HNO3, NO2, NO, HCl, HOCl, H2O2, and COF2, are measured with a very high vertical resolution, a high sensitivity and a high precision.
Also was included in the gondola a piggy back experiment called OFCEAS (Optical Feedback Cavity Enhanced Spectroscopy) . It is an in situ compact analyzer working with a DFB diode laser at 2325 nm, capable of CO and CH4 simultaneous measurements. The high finesse cavity allows effective path lengths of the order of 10 km with a 50 cm long cell (20 cm3 internal sample volume). The instrument performs automatic continuous measurement from ground to ceiling and back, storing the data on flashdisk.
Balloon launched on: 4/20/2011 at 20:35 utc
Launch site: European Space Range, Kiruna, Sweden
Balloon launched by: Centre National d'Etudes Spatiales (CNES)
Balloon manufacturer/size/composition: Zero Pressure Balloon model 150z Zodiac 150.000 m3
End of flight (L for landing time, W for last contact, otherwise termination time): 4/21/2011 at 23:30 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 3 h
Landing site: 185 km SW of Kiruna, Sweden
Payload weight: 520 kg
The balloon flight, -part of the "ENRICHED" project campaign- took place on Wednesday 20 April 2011 from 20:35 to 00:08 UT (22.35 to 2:08 local time). The balloon was launched by auxiliary balloon method and after termination, the gondola touched down at coordinates 66.47°N, 18.87°E at 185 km SW from Esrange base. The recovery of the payload was performed by staff of the Swedish Space Corporation in the morning of the following day, with no damage on the scientific instruments.
One of the main scientific objectives of the flight was to track a large tropical intrusion developing above Scandinavia in the stratosphere from about 25 to 35 km height during the night of 20 April. Another goal of the flight was to make the link with the two previous flights from MIPAS and TWIN in the vortex by observing the mixing between polar air and mid-latitude air in the lower levels (15-25 km).
Due to safety constraints, the measurements were possible only during the slow ascent, lasting about 2h30, from 21:00 to 23:30 UT.
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