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hydrogen chloride, which is formed by chemical processes in the
ozone hole. Thin, elongated tongues of air, known as air mass
filaments, have detached from the polar vortex – very inter-
esting. The tension dissolves; the scientists on board and on the
ground are in high spirits in light of the data sampled.
The hours on the flight back to Cape Town pass slowly.
Tiredness spreads through the cabin. Time for a change;
laughter ripples through the cabin as student Isabell Krisch, who
is using this measurement flight to get a bit closer to obtaining
her Master’s degree, tries on an orange survival suit.
18:30 local time:
After more than 10 hours in the air,
HALO lands safely in Cape Town. At a short debriefing in the
hangar, everyone agrees the effort has paid off. The mission has
been followed in great detail from afar – at the Berlin Air Show.
The flight was followed online for hours. Relief spreads there as
well, when it becomes clear that D-ADLR is safely back. After the
mission, the crew and aircraft have had a lot taken out of them.
Late in the evening in Cape Town, everyone meets for a
beer on the hotel’s roof terrace. The view of Table Mountain
from here is marvellous. Someone remarks: “We have a truly
amazing and exciting job.”
15 September 2012, Cape Town
08:00 local time:
The return flight to Oberpfaffenhofen
takes off two days later, over the Indian Ocean. First, HALO
flies nonstop to the Maldives, past Madagascar and over the
Seychelles. Here, a large storm has to be given a wide berth.
Shortly before leaving the cruising altitude of 14 kilometres,
there is a breathtaking view – the Milky Way, like a painting on
the night sky; countless meteors and sporadic sheet lightning
in a distant tropical storm make for a truly surreal atmosphere.
As the crew lands at Male International Airport, they are
greeted by temperatures of over 30 degrees Celsius. The high
humidity of the tropical air immediately causes condensation
to form all over HALO. The nearly 10-hour flight at high alti-
tude and a temperature of minus 70 degrees Celsius has
completely cooled down every surface. Even the next day,
water droplets continue to fall from the wings.
18 September 2012, Male
08:00 local time:
Three days later, HALO takes off from
Male on the penultimate leg of the journey, over Oman, Saudi
Arabia, Syria and Lebanon, and on to Cyprus. Syrian airspace
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hangar, they start work immediately. Not much is said at this
early hour. The hand movements are almost automatic. Only the
coffee machine in the hangar is not still, running at full speed.
Two units must be filled with liquid nitrogen that will cool the
detectors to a temperature of minus 196 degrees Celsius. And it
was not easy to get liquid nitrogen in Cape Town.
In an office next to the hangar, the latest weather fore-
casts are downloaded from the Internet. The weather towards
the South Pole is good, with no headwind. HALO’s flight to the
edge of the Antarctic continent must be planned in such a way
that, in the event of an engine failure or a loss of cabin pressure,
they can make it back to South Africa safely, at low altitude, by
following the appropriate return flight path. An emergency
landing in Antarctica is not an option – it would be too much of
a risk.
06:00 local time:
The cockpit crew arrives at the airport
from Cape Town. Because of the planned flight time of more
than 10 hours, careful attention must be paid to their maximum
permitted working hours. A sudden wave of anxiety rises shortly
before HALO rolls out of the hangar. Two of the instruments on
board are not working properly. Several colleagues work fever-
ishly on the devices. It is no longer possible to get through the
cabin. There is no unnecessary panic, just no room for any
mistakes. Only bits of what is being said can be made out.
Finally all the equipment is working correctly. The weather has
relented as well – the rain has almost stopped, which makes
things easier. HALO is taken to be refuelled, and the crew must
head to passport control at the other end of the airport. There is
some surprise among the participants, but this flight to Antarc-
tica with no stopover is regarded as an international departure
by the South African authorities.
08:00 local time:
There is a tense atmosphere in the cabin
during take-off. The scientists look at the instrument monitors,
which are showing housekeeping data. Is all the equipment
working properly? After half an hour their faces relax – everything
is OK. As HALO approaches the Antarctic continent more than
four hours later, there is time to take a look out of the window.
The Gulfstream is now flying at an altitude of almost 15 kilome-
tres. Beneath the aircraft, endless ice sheets and several low cloud
fields can be seen. A deep blue sky stretches out above the white
surface, making for a breathtaking view.
The ground team can track the flight path via a satellite
link and stay in contact with the on-board crew. HALO reaches
the air masses of the southern polar vortex. The ozone hole
forms here at this time of year; it is caused by chlorine and
bromine compounds, emissions of which are now banned. The
HALO instruments are measuring an increased concentration of
From the Cape Verde islands in the Atlantic off the coast of West Africa, the route carried on to Cape Town. HALO on the taxiway at Sal
International Airport.
was flown over at the greatest possible altitude for safety
reasons, and the descent to Larnaca only started once over
Lebanon. Two days later, the news broadcast confirm that this
flight plan was exactly the right one; there were heavy air strikes
by the Syrian Air Force in the regions HALO flew over.
19 September 2012, Larnaca
08:30 local time:
The last flight leg takes HALO from
Larnaca, past Crete, over Sicily past the smoking Mount Etna to
Corsica, then turning north to head back to Germany.
16:00 local time:
HALO lands at its home airport in
Oberpfaffenhofen.
Thanks to meticulous logistical preparation, the commit-
ment of all those involved and a bit of good luck, HALO was able
to demonstrate its outstanding capabilities on this first major trip.
Even with all the external instrument attachments, the research
aircraft travelled at altitudes of up to 15 kilometres for long
stretches – as far and high as had been dared to think possible
during the aircraft’s design phase many years earlier. Also, HALO
proved itself to be very reliable; it was possible to take off for
every flight according to plan.
At the end of the ESMVal mission, everyone involved met
up in the hangar in Oberpfaffenhofen for a final debriefing. This
measurement campaign had been planned for a long time.
Numerous technical and logistical problems had to be overcome.
But now there are happy faces all around, without exception.
Bring on the next mission…
•
About the authors:
Hans Schlager is head of the Atmospheric Trace Species
Department at the DLR Institute of Atmospheric Physics in
Oberpfaffenhofen and leads the ESMVal flight missions.
Steffen Gemsa is a member of the DLR Flight Experiments
Facility in Oberpfaffenhofen and is a DLR test pilot.
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The HALO cockpit during the mission – even for DLR test pilot Michael Grossrubatscher, it was
a very special mission.
From a cruising altitude of 15 kilometres, the cur-
vature of the horizon is discernable.
Diversion on the night flight – fashion
show in a survival suit
HALO lands in Cape Town. The measurement flight over
the Southern Ocean is complete.
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