This week's topics:

• Space tourist coming home
• Noctilucent clouds - cold clouds that are hot again 
  

Pulsar mission nearing its end – fifth space tourist coming home
Charles Simonyi was indeed launched aboard Soyuz TMA-10 from Baikonur on 7 April. On the third orbit I could pick up the voice of the Russian crew with a handheld ICOM R-20 receiver here in Sweden. On this particular pass they had a minor nuisance in talking to the ground station and you can hear them calling mission control in Moscow (“TsUP”) using their call-sign “Pulsar” (listen here) and not receiving an immediate reply.

Later everything went smoothly and Mr Simonyi will return from the International Space Station in the Soyuz TMA-9 spacecraft docked to the station since 20 September 2006. ISS long-term crew members Mikhail Tyurin and Michael Lopez-Alegria will accompany the space tourist home on April 21. The landing was delayed a day and moved farther south because wet ground at the initial site in Kazakhstan precluded helicopter operations there. Welcome home to the fifth space tourist. In a few years suborbital space tourists will be so commonplace that only local media will take notice of these space travelers taking off from place such as SpacePort America and Spaceport Sweden.

Noctilucent clouds - an old topic for Swedish space activities - "hot" again!
On April 25 NASA will try to launch the Aeronomy of Ice in the Mesosphere (AIM) spacecraft with a Pegasus rocket from the Vandenberg Air Force Base, California. AIM is the first mission dedicated to the exploration of mysterious ice clouds at the edge of space in the Earth's polar regions. These clouds have grown brighter and more prevalent in recent years and some scientists suggest that changes in these clouds may be the result of climate change.

AIM will study this phenomenon typically observed at approximately 80 kilometers altitude. These clouds form in the summer at high latitudes because of the extreme cold in this region of the so-called mesosphere. The mesosphere is the region just above the stratosphere. When observed from high latitudes these clouds scatter light from the sun which is slightly below the horizon in the north and illuminates the clouds while the observer on the ground is in darkness. For this reason these clouds are called night-shining clouds or noctilucent clouds, abbreviated NLC.

How these ice clouds actually form is not completely understood and neither are the reasons behind their increased appearance at lower latitudes or why they have recently grown brighter and more
frequent.

NLC have been a main topic in Swedish space research since the very earliest days of space activities in Sweden. The first ever rocket launched into space from Sweden on 14 August 1961 tried to create an artificial noctilucent cloud by injecting a cloud of talcum powder at 80 km altitude (see picture on the right). The idea was, i.a., to compare the optical properties of this man-made cloud with those of real NLC.

Two years later rockets launched from the temporary rocket base at what is now known as the Vidsel Test Range measured the temperature at 80 km altitude while NLC were observed. It turned out that there is a temperature minimum of down to -143 ^oC at this altitude – neatly explaining why the clouds appear there.

These first sounding rocket launches from Sweden were joint projects between NASA and the Institute of Meteorology at the University of Stockholm. A predecessor organization to SSC, the Space Technology Group ran the rocket campaigns. I myself was a rocket assembly technician during these launches – at the age of sixteen! Later rocket flights from Esrange determined that the particles are basically ice particles with a diameter of about 0.1 μm.

Since the sixties NLC research has continued in Sweden, also with the Odin orbital observatory, which studies NLC on a routine basis. A sounding rocket, PHOCUS, will be launched from Esrange next year to study NLC. Little did we realize in 1961 that noctilucent clouds would be a “hot” climate topic forty-six years later!

Best Wishes

Sven Grahn