STRATOSPHERIC BALLOON BASES IN THE WORLD

The first steps of Sweden in the space field occured in the early 60's. At that time, several rocket launch campaigns were conducted to study the so-called "noctilucents clouds" from Kronogard located in the north part of the country.

Alongside these pionnering efforts and consistent with the initial experience of other European countries, in 1962 was created the European Space Research Organization (ESRO) forerunner of the current European Space Agency (ESA). The first initiative undertaken was the establishment of a sounding rocket research programme, which needed a permanent facility to perform the launches.

After excluding other locations such as Salto di Quirra (Sardinia), Narssarssuaq (Greenland) and Andoya (Norway), the final choice was for a desolate landscape in the Swedish Laponian area close to the Arctic Circle and a few kilometres west from the small town of Kiruna. The site was baptized ESRANGE (acronym for European Space Range).

The construction work started in 1962, and was not finished until 1966, the year of its formal inauguration. The first rocket was launched from there a year later, starting the regular activity involving scientists from several countries.

In early seventies ESRO was engaged in the construction of a space centre in Kourou, French Guiana casting a shadow of doubt about ESRANGE's future. In a risky and bold move, between 1971 and 1972, after assuming that was not profitable to "reconvert" the center for other purposes (its transformation into a tourist destination, or to use it as a clinic for the treatment of alcoholics, among other possibilities), the Swedish government take over the operation of the facility, creating for this purpose the Swedish Space Corporation (SSC).

During the early years in Swedish hands, was clear that would be difficult the maintainance and updating of the base, so in 1973 was decided to diversify their activities first trying to establish a satellite tracking station and second offering the facilities to the international scientific community to launch stratospheric balloons. Its privileged position is ideal to carry out circumpolar balloon flights to send complex scientific experiments to study the different atmospheric variables of the Arctic.

Despite that previously had been made some isolated balloon flights, between January and March 1974, took place the first organized balloon launch campaign. It was called SAMBO 1 and involved the coordinated participation of the French space agency CNES and his Russian counterpart of IZMIRAN. The aim of the initiative was to make stratospheric measurements of the spectrum of auroral X-ray emission at high latitudes.

To this succesfull campaign followed in subsequent years several more in collaboration with Universities and Scientific Centres of various countries. At the same time to allow a greater flight duration, agreements have been signed to allow the overflight, landing and recovery of gondolas in neighbouring countries such as Finland, Norway and Russia. Recently was added too the choice to perform transatlantic flights to Canada as well.

So, after more than 30 years of activity in the scientific ballooning field, and with 550 launches in their record, ESRANGE had become the most important stratospheric balloon launch base of Europe. Several campaigns performed there in the past had a duration of several months and involved up to 40 launches each.

The geographic location of Esrange, at 67 deg 56 min N and 21 deg 4 min E, offers several unique advantages for launching of stratospheric balloons:

• the location is excellent from a scientific point of view, for experiments related to auroral research, astrophysics and other high latitude phenomena as the ozone depletion in the atmosphere, validation of polar orbiting satellite experiment
• testing of space systems including drop tests of free falling objects can be performed in the Esrange impact area for sounding rockets,
• a vast area covering the northern parts of Finland, Norway, Russia, Canada, Alaska and Sweden is available for land recovery of experiments,

On regards the winds regime balloons launched during the winter period can be easily injected into the polar vortex. The predominating stratospheric winds are rather strong from W to NW which gives 2-5 hours of ceiling time and with recovery of the payloads either in Finland or Russia.

During the summer period from mid May to mid July the strtospheric winds are very stable from the east, which makes that period very suitable for medium to Long Duration Balloon (LDB) flights including Transatlantic flights. During this period the latitude excursions are not expected to exceed +/-3°.

Finally during the turn-around periods in late April and early May and second half of August the stratospheric winds are very low and irregular which means that the payloads can be within the range of the base up to 3 days.

Note: in this section we will be refering only to the specific infrastructure to launch balloons.

Initially the base had an asphalt launch area pear shaped about 400 meters long and 250 meters wide, situated about 150 m south of the base's Main Building.

In Summer, 2004 a major extension of the entire launch field was done so today the total launch pad area is 250.000 square meters as can be seen in the image at left (click to enlarge). It was modified to allow launching balloons in different directions, divided into six runways acting as corridors near 200 meters in length, aligned with the common direction of the prevailing winds in differents seasons of the year. The entire launch field is covered with fine gravel and at its center lies a cavity containing electrical power, ground cables, public address loudspeakers, and a telephone line.

This expansion is directly related to an agreement signed with NASA, by which in 2005 the American agency began to use the site in summer to launch stratospheric balloons in transatlantic flight. The balloons after release, reach float altitude and are caught in the westward streams flying over Sweden, Norway and then crossing the North Atlantic Ocean. When the balloon reach the northamerican continent the flights are terminated in northwestern Canada.

The increasing of the launch capabilities lead to the acquisition in 2004 of a new launch vehicle which was built by a local company in Kiruna. The 40 Tons. Volvo truck was nicknamed "Hercules" and replaced the old crane formely used to hold the bigger payloads. With a highly manouvering arm the truck allow to manage in a much more efficient way larger payloads (up to 6000 lbs) so along with the enlarged launch pad the facility can launch balloons up to 1.000.000 cubic meters of volume, the bigger standard balloon in use today. At right we can see the new vehicle in action while holding the BLAST telescope during a rehearsal of the first transatlantic launch in 2005 (click to enlarge).

Located on the north side of the balloon pad, there are three large buildings for balloon and payload preparations.

The first building known as "Cathedral" have a payload preparation area of 300 square meters with a ceiling of 7 meters and an overhead traveling crane, with a lifting capability of 3.2 Tons. The area floor is heated and vented to allow a confortable temperature and prevent dust accumulation. The back of the building is a two floor office area to be used by scientific teams during campaigns.

The second building nicknamed "Chapel" have a balloon payload assembly hall near 100 square meters with additional storage and two offices. It is equipped with an overhead crane of 1 Ton. which can be extended 2 m outside the entrance door. A 30 square meters area is used as storage for launch support equipment. One room in the Chapel is used as a preparation room for EBASS, the SSC telemetry and telecommand system for support of balloon flights.

The third building is known the "Basilica" and is designed for preparation of the flight train. The main assembly hall is 308 square meters equipped with a crane with a 1 Ton. lifting capability. The front part of the building is a two floor area with an office and an Operation Balloon Center on the second floor, used only during count down and the launch phase.

A fourth large building is located near the "Basilica" and is used for storage during balloon campaigns and also houses the launch vehicle "Hercules".

Due to increased demand for launch services in last years, SSC decided in 2010, to start the construction of another building for integration of rocket and balloon payloads. This new building was built close to the existing facilities in the balloon launch pad area and counts with an area of 795 square meters. It was inaugurated in May 2011.

The base also counts with mechanical and carpentry workshops, and several laboratories including chemical, biological, electronic and a clean room area.

On regard communications and telemetry systems, today, ESRANGE have two choices: EBASS and E-Link. In 1998 SSC and DLR decided to develope a Telemetry/Telecommand (TM/TC) service system for stratospheric balloons. To reduce developing costs the new design was based on DLR's MFB (Multi Function Board) which is in use on Maser sounding rockets and on the Express satellite. The system was named EBASS (Esrange Balloon Service System) and includes all necessary functions to perform GPS position determination, cut-down on command and cut-down by timers, top valve and ballast machine operations for balloon piloting. It counts with a transmiter/receiver system based on FM with a nominal data bandwidth of 38.4 kbps and a serial interface. With an output power of 2.5 W it was developed in two versions: a light one weighting 17 kg and the heavy one nearing 30 kg. Total operation time is near 60 hours and until today it was worked flawlessly in more than 45 missions.

On the other hand E-Link (Esrange Airborne Data Link) is a telemetry system that offers a simplified interface based on standard Ethernet architecture. It can handle TCP/IP and UDP/IP communication with high bandwidth across long distances. The system handles also other types of synchronous and asynchronous user interfaces. E-Link was qualified recently and works on S-Band with a maximum output power of 10w and a duplex data bandwith of up to 2Mbps. It weights 11 kg (including batteries) and have a nominal operation time of near 12 hours.

In the case that the balloon mission involves the drop of test vehicles and probes, the base counts with a a vast restricted impact area on land (5200 square kilometers) originally created for sounding rockets, but also available in such cases. Also a second launch area -under ESRANGE's control too- is located at the airport in the nearby town of Kiruna. It consists of a giant hangar used to house scientific planes which are involved in Arctic research at ESRANGE. The site called "Arena Arctica", has sometimes been used for inflation and subsequent launching of small superpressure stratospheric balloons as we see in the picture at right.