On Monday, March 24th, 2014 the ML-CIRRUS Mission officially started after several months of intense preparation. From the very beginning of this project enviscope GmbH and Gomolzig Flugzeug- und Maschinenbau (GFM) accompanied the various scientific institutions in instrument design, manufacturing, documentation and airworthiness certification for the german special mission aircraft HALO (Gulfstream G550, D-ADLR). Now, we can proudly announce that this rather complex process has been finished, that all instruments passed the certification in-time. All instruments performed well during EMC- and test-flights.

The aim of the ML-CIRRUS mission is to investigate nucleation, life cycle and climate impact of natural cirrus and aviation induced cloudiness in the mid latitude tropopause region in Europe and the North Atlantic. During March and April 17 measurement flights have been accomplished, all starting from Oberpfaffenhofen (Germany). To fulfil the various scientific tasks, several instruments and inlet systems had to be built, tested, and certified. Those systems, for which enviscope and GFM made a major contribution are described below.

Inlet Systems

For the different scientific questions special air intake system have been designed for HALO and installed for the ML-CIRRUS mission:

  • The Trace Gas Inlet (TGI) was designed and built on behalf of  DLR-FX. It is a multipurpose intake for ambient air for the investigation of trace gases. Four TGIs with different configurations are attached to the upper fuselage to supply ambient air to the various analytic instruments within the cabin.
  • The shrouded Counterflow Virtual Impactor (CVI) was designed in co-operation with the Institute for Tropospheric Research in Leipzig (TROPOS). In combination with the CVI-Rack installations it is used for the sampling of cloud residual particles. The size spectrum of particles entering the inlet can be controlled by generating a counter flow at the inlet tip.
  • The HALO Aerosol Standard Inlet (HASI) has been designed on behalf of IPA DLR to sample ambient aerosol particles and to route them to cabin instrumentation. To reduce particle losses on the way from inlet to the instrument, special focus has been put on a minimal bending of the tubing.
  • The HAI Inlet (Hygrometer for Atmospheric Investigations), by order of the Research Center Juelich, represents an open path inlet for water vapor measurements. The laser light beam is folded by mirrors between the two pylons to achieve an optical path length of 4.8 m.

Additionally three optical inlets for solar irradiance and radiance measurements (SMART) have been installed. Two irradiance optical heads have been mounted on horizontally stabilized platforms SPARM. This project has been accompanied by enviscope for many years and has now been finalized which makes a "long-held dream come true".


HALO shortly before start to the first test flight of the ML-CIRRUS Mission

HALO shortly before take-off for the first scientific test-flight of the ML-CIRRUS mission.


Besides design and manufacture of all the shown inlet systems, enviscope/GFM was also responsible for the certification of CVI, HASI and HAI. All of them passed the design and qualification process. The required certification, classified as a Major Change to the aircraft, could be finalized after the test-flights and the Luftfahrt-Bundesamt (LBA) issued the Supplemental Type Certificates (STC). With these approvals the inlets now can be used as basic equipment of HALO in future missions.


Cabin installations

Besides the inlet systems, enviscope/GFM also provided support for our customers by the adaptation, integration, and certification of  various scientific instruments into the cabin. A total of six instrument racks, which enviscope/GFM have worked on, were installed into the HALO cabin. The instrumentation of three modifications (HALO_HAI-I, HALO_FISH and HALO_FAIRO) are combined in one HALO standard rack, the two modifications HALO_SNOOPY and HALO_SMART share one rack.




Modification Scientific instrumentation Inlet Scientific background Responsible Institution contribution of enviscope/GFM
Optical particle counter
number and concentration of ice nuclei
Institut für Atmosphäre und Umwelt – University of Frankfurt
documentation and certification
Multi channel spectrometer
radiance, irradiance
Leipziger Institut für Meteorologie (LIM) – Universität Leipzig
development and design of SPARM, design of SMART instrument housings, documentation, certification.
water vapor mixing ratio
Institut für Energie- und Klimaforschung (IEK-7) – Forschungszentrum Jülich
rack integration, documentation, certification.
Single particle soot photometer
mass and concentration of soot aerosols
Institut für Physik der Atmosphäre (IPA) – DLR
rack integration, documentation, certification.
Tunable diode laser absorption spectroscope
water vapor mixing ratio
Institut für Energie- und Klimaforschung (IEK-7) – Forschungszentrum Jülich
design of instrument housing, documentation, certification
Chemical ionization mass spectrometer
water vapor, trace gases (SO2, HNO3, HNO2, HCl)
Institut für Physik der Atmosphäre (IPA) – DLR
rack integration, documentation, certification
Ozone analyser
atmospheric ozone
Institut für Meteorologie und Klimatologie (IMK) – Karlsruher Institut für Technologie (KIT)
rack integration, documentation, certification
Condensation particle counter, absorption photometer, aerosol spectrometer
droplet residual
Leibniz-Institut für Troposphärenforschung (TROPOS) – Leipzig
design of instrument housings, rack integration, documentation, certification
PMS Rack Unit
Power distribution and data communication for PMS carrier
Institut für Physik der Atmosphäre (IPA) – DLR
design of instrument housings, rack design and integration, documentation, certification
Dropsonde Rack Unit
Storage, telemetry, and data acquisition for dropsondes
Institut für Physik der Atmosphäre (IPA) – DLR
rack integration, documentation, certification


The PMS Rack Unit (HALO_PRU) was developed to provide power distribution,data acquisition, and a user console for the operation of sensors in the underwing PMS carriers. Special instrument housings have been developed to carry these data aquisition and power supply components.The low profile rack was designed to be mounted nearby an emergency exit and represents now an alternative for the HALO standard instrument rack.




We thank our customers and all involved parties, especially the LBA and both Design Organisations of DLR and GFM, for the good collaboration. We are happy that it is planned to continue this close collaboration between GFM, enviscope, and DLR in the future with engineering and certification work for a number of scientific instruments to be operated aboard HALO. Now we are satisfied to have accomplished the plans and collaborations for ML-CIRRUS successfully and are looking forward to the next challenge ACRIDICON.