In August-September 2009 American space shuttle STS-128 performed its mission at the International Space Station.
The STS-128 crew delivered several letters addressed to Russian cosmonaut Roman Romanenko, a member of Expedition 20.
First this letter was sent from Vienna, Austria to Houston, USA by registered mail.
The most interesting is that the letter addressed to the International Space Station was sent at the day of the 40th anniversary of the first manned step onto the Moon surface, on July 21, 2009, in according to European time. When Neil Armrstrong stepped onto the Moon it was July 20 in the USA, but in Europe it was already July 21.
Having been delivered to Houston, the letter was handed over to the STS-128 crew. Then it was delivered to the ISS.
Aboard the ISS, the addressee, Russian cosmonaut Roman Romanenko postmarked the letter with the ISS board post mark dated August 30, 2009, the day when the shuttle docked with the ISS. The letter was also marked with the ISS octagonal board souvenir seal.
One of the Austrian postage stamps shows the launch of Apollo 11 which delivered the first crew to the Moon. Another Austrian postage stamp shows the ISS.
So, this letter is a rather interesting astrophilatelic document.