ESA Earth Observation Image: JAXA ALOS satellite views Helsinki

This image acquired by Japan’s ALOS satellite on 28 June 2009 shows Finland’s capital and largest city, Helsinki (upper right), on the shores of the Gulf of Finland.

The gulf is the eastern arm of the Baltic sea, stretching all the way to St Petersburg in Russia.

The waters are relatively shallow, with an average depth of about 38 m and maximum depth of about 100 m.

During winter, usually in January, the waters freeze and stay frozen until about April.

Satellites play an important role during this season for shipping, providing imagery that helps icebreaker boats navigate through these frozen waters.

Situated on the tip of a peninsula and on more than 300 islands, Helsinki is sparsely populated compared to other European capitals and has many green areas.

Running north to south through the centre of the city is a 10 km-long forested park that offers opportunities for outdoor sports and activities to Helsinki’s residents.

This year, the park celebrates its 100-year anniversary, marked by various activities including nature walks, a photo competition and other events.

North of the city we can see the runways of the Helsinki airport, while farther west, the large, dark green area of Nuuksio National Park is evident.

The image is featured on the Earth from Space video programme.

ESA CubeSat Space Tethers need to be Snap-proof

Space tethers hold intriguing potential for satellite manoeuvring, attitude control and even power generation. 

Unfortunately, about half of all orbital tether tests have either failed to deploy or snapped, probably due to micrometeoroid impacts.

ESA is developing on a new snap-proof design for their ongoing Satellite program.

Scanning-electron microscope image of the new design of an ultra-thin  snap-proof solar sail tether.

The tether is soon to be operationally tested on Estonia's ESTCube-1, which is being launched into orbit along with ESA's Proba-V satellite on the next Vega rocket.

Harnessing manufacturing techniques from the microelectronics industry, this aluminium tether measures just 50 micrometres across - across half the diameter of the average human hair - with a smaller 25 micrometre wire interweaved onto it.

The University of Helsinki's interweaving technique, with several wires joined together every centimetre, will hopefully keep the tether intact to run an electric charge down it, even if all but one subwires in the tether are cut.

Designed, built and operated by the students of several Estonian universities and led by the University of Tartu with Tartu Observatory, ESTCube-1 is part of ESA's Plan for Cooperating States (PECS) agreement with Estonia.

PECS is a one-year programme of activity taking place as a prelude to the country joining ESA as a Member State.

The electric solar sail, or 'E-sail' being tested by this CubeSat mission, passes electricity through wires such as these to generate electrostatic forces which in turn generate momentum.

In low orbit, E-sails could be used as brakes to deorbit satellites. Beyond Earth's magnetic field, satellites could one day make use of the solar wind to gain a nearly free ride across the Solar System.

ESTCube-1 will unfurl a 10 m-long single-strand E-sail to show its potential as a compact and economical deorbiting method, measuring the resulting force acting on the E-sail as it comes into contact with space plasma.

A 100 m E-sail tether will fly on Finnish student CubeSat Aalto-1 next year. Artist's impression shown below. The thin E-sail tether line is visible in the picture.