The HALO project is based on an initiative of the entire German atmospheric
science community. It was found that the acquisition of a modern research
aircraft is essential to continue the successful research and maintain the
leading position of German scientists for the next decades in this area.
DLR (Deutsches Zentrum für Luft- und Raumfahrt) and MPG (Max-Planck-Gesellschaft)
took the lead and submitted the application for this major research facility
investment. This project is supported by scientists from 31 institutes. The
HALO proposal was evaluated by the scientific advisory body of the Federal
Government (Wissenschaftsrat) who recommended the realisation of HALO without
In September 2004 the German ministry of education and research has approved
the construction and modification of this high-performance research aircraft.
The costs of the HALO aircraft will be covered by contributions from the Ministry
of Education and Research, the Helmholtz Association and the Max-Planck Society.
HALO will be based on a GulfstreamG550 - a large business jet. However before
the aircraft will take off for the study of scientific questions it will undergo
significant modifications that transform the luxury passenger aircraft into a
The concept behind HALO is to provide an optimal platform for airborne atmospheric
science and Earth observation, a well-equipped flying laboratory that allows the
scientists onboard to completely focus on their own experiment.
A large set of jet aircraft candidates was investigated for its suitability. Finally
the business jet aircraft G550 of Gulfstream was found to meet best the essential
requirements of the future HALO users:
The main strengths of the proposed HALO aircraft are its long range and endurance,
high ceiling altitude and large instrument load capacities, which are not available
in such combination on any other research aircraft in Europe.
- range well above 10000 km or more than 10 flight hours for transcontinental
experiments and long duration measurements;
- certified ceiling of more than 15 km,
- maximum payload of 3 tons,
- a large usable cabin area of 20-30 m2 for simultaneous operation of several
complementary instruments and scientific personnel from several groups (for
multidisciplinary and international projects),
- potential for quick modifications for a wide variety of applications and for
flexible use as research aircraft with different instrument configurations for
various research projects.
HALO provides the opportunity to carry out measurements in areas that can currently not
be probed by other platforms. This includes nearly the full altitude range of the
troposphere and lowermost stratosphere and remote parts of the Earth. It can carry
comprehensive payloads for simultaneous observation of a large set of species.
In order to be a suitable platform for environmental research, HALO has to provide
certain mechanical and electronic interfaces that need to be added to the basic aircraft.
These modifications of the aircraft frame, electronics, avionics, and sensor systems
are prerequisite to operate any scientific instrumentation on HALO. In order to simplify
the transfer of existing scientific equipment, it is planned to copy many standard
interfaces from the most popular research aircraft in Europe, such as the DLR
Falcon. Examples for this are openings and certain hardpoints on the aircraft
fuselage, experimental power distribution concepts and many standard sensors
that will be permanently installed on the aircraft. However, over the past years
many additional requests for modifications came up, which would allow the scientists
to use sensors or combination of sensors that could not be operated on the existing
aircraft before. The final decision on the modifications of HALO will be subject to a
meeting of the future users to bring their needs down to a common denominator, which
is constrained by financial aspects as well as the possibilities of the aircraft
manufacturer. HALO will carry a basic sensor package and data acquisition
system in order to provide a complete set of meteorological and aircraft
data to each user. The envisaged sensor package on HALO will be more complete
than the ones on the present research aircraft and it will use new sensor
concepts and better sensor equipment.
HALO will represent a major improvement in the airborne research capability
for research institutes and universities to study atmospheric phenomena and
their interactions from local to global scales. Aircraft measurements are
particularly valuable to describe processes at the scales of transport and
photochemistry. The observed spatial variability in clouds, aerosols, water
vapour and ozone, for example, ranges from less than 100 m (turbulence) to
more than 1000 km (synoptic weather systems). Since oxidation processes in
the atmosphere proceed through radical reaction chains, chemical measurements
must typically be performed at a time resolution of seconds to minutes.
HALO would especially enable studies of the chemistry and dynamics of the
upper troposphere and lower stratosphere (UTLS) between about 8 and 15 km
altitude. The certified ceiling of about 15 km would enable wide-ranging
coverage of the UTLS region from the subtropics to the poles.
Because of its relatively large size, HALO would facilitate the deployment of
comprehensive sets of instrumentation, as developed within Germany or
elsewhere, to simultaneously measure physical and chemical parameters
to characterise transport, radiation and chemical processes. Furthermore,
the long range and high altitude performance would greatly increase
the fraction of the global atmosphere in which fundamental physical
and chemical processes could be directly observed.
Improved process understanding from aircraft measurements contributes
to the development of meteorological and climate-chemical models. These
models serve to study complex interactions and feedbacks, and to perform
sensitivity studies and scenario-based predictions. Confidence in models
can only be established by showing that processes are well reproduced at
all relevant scales. Satellite images, on the other hand, provide generally
only a two-dimensional picture of the atmosphere, and at fairly coarse
resolution. Aircraft measurements provide the required three-dimensional
resolution, and they can be linked with satellite images to construct a
more complete view at regional to global scales. Intensive field measurement
campaigns with the HALO aircraft would be guided by model forecasts
and (nearly) real-time satellite images to plan flight tracks and to
independently test models and remote sensing retrieval algorithms.
From the planned measurement campaigns with HALO scientific achievements
are expected in nine major research fields:
Although the first scientific missions will not be performed before 2009
a specific planning of the sequence of flight missions for the various
scientific questions has already started. This lead time is necessary to
initiate the development of new instruments and to adapt existing
instruments for the use on HALO.
HALO will be open to German as well as international users.
- Atmospheric chemistry and global pollution
- Atmospheric dynamics and transport
- Cloud research
- Meteorological research
- Climate research
- Global carbon cycle
- Polar Research
- Earth Observation
- Geophysics and Geodesy