Purpose of the flight and payload description
MACSIMS was the acronym for Measurement of Atmospheric Constituents by Simultaneous Ion Mass Spectrometry. It was an instrument developed in early 90's that incorporated a double focusing Mattauchherzog magnetic mass spectrometer and an octopole ion guide. It was aimed to obtain simultaneous in-situ measurements of nitric acid and dinitrogen pentoxide in the stratosphere, using the active chemical ionization technique. It was built and operated through a collaboration between the Physikalisches Institut of the Universität Bern, from Switzerland, the Laboratoire de Physique et Chimie de l'Environnement (LPCE) of the University of Orléans and the Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB).
In the image at left we can see a picture of Macsims on its gondola (click to enlarge). It consisted of three major parts: an ion production package, an ion transport system, and an ion analyzer part. The ion production package contained the ion source block in which several ion sources were integrated, the gas bottles with the ion source gas mixtures, the valves and gas circuitry elements that controled the flows of the different ion source gases and the switching between the different ion sources, and the electronics (power supplies and microprocessor) to control the ion sources.
In the active chemical ionization method primary ion species were injected into a flow tube with ambient stratospheric air. The primary ions were selected to produce characteristic secondary ions from ion-chemical reactions with the neutral gases to be detected. At the end of the flow tube, after a flow-time of about 30 ms, primary and secondary ions were analyzed with the double focusing mass spectrometer capable of measuring a full spectrum part simultaneously with the use of two electro-optical detectors.
Profiles of HNO3 were determined using the conversion of chlorine cluster ions, generated by a discharge, into N03 clusters. Additionally the products from ion clustering reactions of CO3, produced by a photo-electron source, allowed an independent determination of a nitric acid density profile. In order to detect N205 (and ClONOZ), negative iodine ions were used.
A more detailed description of the instrument and measuring methods can be found in the references at the end of this page.
Details of the balloon flight
Balloon launched on: 11/23/1995 at 20:18 utc
Launch site: Virgen del Camino Airport, León, Spain
Balloon launched by: Centre National d'Etudes Spatiales (CNES)
Balloon manufacturer/size/composition: Zero Pressure Balloon model 100z Zodiac - 100.000 m3
Balloon serial number: 100Z Nº 60
End of flight (L for landing time, W for last contact, otherwise termination time): 11/24/1995 at ~ 01:45
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 5 h 32 m
Payload weight: 775 kgs
Gondola weight: 423 kgs
The balloon was launched using auxiliary balloon method at 20:18 utc on 23 November 1995 from the Virgen del Camino airport near Leon, Spain. After having reached a ceiling altitude of 32.1 km, where the balloon was kept for about 50 min, a slow descent was started at a velocity of 1.2 m/s down to about 18 km. No technical problems occurred in flight and measurements could be made in the altitude range 32 to 18 km. As a result of the microprocessor control of the instrument and the preprogramming of the different measurement tasks, mass spectra could be recorded continuously during the balloon descent.