ISO prior to transfer to the Ariane launcher gantry, at Europe's spaceport in Kourou
ISO prior to transfer to the Ariane launcher gantry, at Europe's
spaceport in Kourou
ISO mounted on the Ariane launcher prior to closing of the fairing
Lift-off of the Ariane 44P carrying ISO from Kourou
ISO is the world's first true astronomical observatory in space operating at infrared wavelengths. It will provide the scientific community with an unprecedented opportunity - the only one for the next 10 years - to observe a wide variety of weak infrared radiation sources, such as cold gases, galaxies and stars dying and being born.
Teams of astronomers have already begun receiving data from many cosmic sources. Those preliminary results confirm ISO's uniqueness as an observatory.
When a moderate-sized star dies, it releases a cloud of chemical elements into space called a planetary nebula. These ISOCAM images of the planetary nebula NGC 6543 illustrate ISO's unique ability to range freely through the infrared wavelengths.
At 10.5 microns, ISOCAM sees emissions from charged sulphur atoms, giving the nebula a spherical appearance. At 12.8 microns, it sees radiation from charged neon atoms which gives the nebula an elongated shape. At 15 microns, arms of warm dust protrude in various directions as the ejected matter interacts with material released from the star earlier.
The spectrum from the Short-Wavelength Spectrometer shows the intensity of emission at each wavelength. Sulphur and neon are present. The 'hump' is due to warm dust in different parts of the nebula, at low but variable temperatures.
Different impressions of a dying star
The ISO Short-Wavelength Spectrometer diagram
The ISO camera, called ISOCAM, has obtained this infrared image of star formation along the spiral arms of a galaxy 20 million light-years away.
The Whirlpool Galaxy, catalogued as M51 or NGC 5194, is a relatively near neighbour of our own galaxy, the Milky Way. While it is smaller and less massive than the Milky Way, it is much brighter due to recent intense star formation. Historically, it was the first 'spiral nebula' identified by astronomers. While very detailed images have been available for some time in the optical and radio wavelength range, infrared data in the ISO range has been very limited. In this image, not only the spiral structure but also details within it are easily visible.
Bright spots in the spiral arms correspond to warm dust clouds where star formation is proceeding on a large scale. Those areas are linked by regions of cooler dust along the spiral arms and in the spaces between the arms, where previous generations of stars have left their debris. The spiral arms can be traced right into the heart of the galaxy, where there are hot spots of star formation on either side of a bright central nucleus.
A companion galaxy (NGC 5195), at the top of the image, appears much smaller than it does by visible light because starmaking is concentrated near its nucleus.
Since its launch on 2 December 1995, SOHO, ESA's Solar Heliospheric Observatory, has been heading towards its vantage point at 1.5 million kilometres from the Earth. From there, it will probe the interior of the Sun, addressing many fundamental questions about the star.
Two and a half months after the launch, the mission objectives are all being met or exceeded. The spacecraft has been checked and found to be in excellent condition. Specific tests on data transmission and microdisturbances (jitter), which have recently been completed, have confirmed that the environment and services offered to the scientific payload are exceeding specifications.
The scientific payload of 12 European and American experiments, covering three solar physics disciplines (solar atmosphere remote sensing, helioseismology, and solar wind investigations in situ), has been fully switched on following a quiescent period. That interval was planned to allow a complete outgassing of volatile substances to take place without affecting the instrument's final cleanliness.
All instruments have, where applicable, seen their 'first light' and are in some cases already gathering scientific data.
A major midcourse correction manoeuvre, executed on 4-5 January, has put SOHO on an optimised path towards its final orbit around the Lagrangian point L1. The injection into that halo orbit is planned for 14 February.
Further instrument and spacecraft calibrations and interaction testing will be carried out in the coming weeks, leading to the conclusion of the commissioning of the spacecraft and its payload - and the beginning of the main observation programme - at the end of March.
Arrival of the SOHO spacecraft and associated equipment a total of 59 tons at Kennedy Space Center (KSC) in Florida on 1 August for the start of the launch campaign
The SOHO spacecraft during the final solar-array deployment tests
at KSC. The truss in the foreground was used to compensate for
the effects of gravity on the deployed wing
The encapsulation of SOHO beneath the fairing of the Atlas-2AS
launcher on 9 November
SOHO being lifted to the top of the Atlas launcher
The first 5 minutes of the Atlas's flight, captured in a long-exposure image
Lift-off at 3.08 Eastern Standard Time on 2 December, as SOHO
starts its long voyage to the Lagrangian point (L1) between Earth
and Sun
Thomas Reiter, the ESA astronaut who has been on board the Russian space station Mir for more than five months, made his second Extra Vehicular Activity (EVA) or 'spacewalk' on 8 February. He made his first one last October when he installed an experiment, the European Space Exposure Facility, on the exterior of the station, as part of the EuroMir mission. He became the first ESA astronaut to perform a spacewalk.
One of the EuroMir astronauts working at the end of a manually-operated
telescopic arm used to reach the work site
The Russian space station Mir in orbit. It has a modular
construction, with four scientific modules docked to the core
habitation module
During the recent four-hour outing, he and a Russian cosmonaut recovered two cassettes from the facility. The cassettes had been collecting cosmic dust and man-made space debris. They can be opened and closed by remote control from within Mir. One had remained open throughout most of the mission, the other had been opened only when the Earth passed through the trail of dust left behind by comets.
They also installed a new cassette which was successfully tested during the EVA. Thomas Reiter will carry the experiment cassettes with him when he returns to Earth at the end of February.
Space scientists are eagerly awaiting them in order to study their contents. The results of the experiments should provide a better understanding of the composition of the microscopic debris that clutters low Earth orbit. This information is important for the design of the International Space Station; it will have to withstand constant bombardment by the tiny particles. Scientists will also investigate how much of the debris is man-made and how much is naturally-occurring cosmic dust. The contents of the casettes will provide the first opportunity to study cometary material in the laboratory.
From the many television and voice transmissions to Earth, Thomas Reiter appears to be in very good spirits and at ease aboard Mir, his home and workplace since 5 September 1995.
The 180-day EuroMir 95 mission will end on 29 February, with the Soyuz capsule landing in Kazachstan, Russia. A new crew is scheduled to travel to Mir on 21 February.
Two ESA astronauts, Claude Nicollier and Maurizio Cheli, will be onboard the Space Shuttle 'Columbia' when it blasts off on a unique mission that could open a new era of space tether operations.
The ESA astronauts who will fly on the Tethered Satellite System
mission: Maurizio Cheli (left) and Claude Nicollier (right)
During the 14-day mission (STS-75), a Tethered Satellite System (TSS) will be deployed for the second time and the US Microgravity Payload (USMP) will be flown for the third time. The launch is scheduled for 22 February and the landing for 7 March.
Tethered satellite to be deployed
The TSS project
is a joint effort of the Italian Space Agency (ASI) and NASA. The
satellite, weighing 518 kg and measuring 1.6 metres in diameter,
will be deployed on the end of a conductive tether that is 20.7
km long and only 2.54 mm thick. One goal is to demonstrate that
a satellite can be deployed, stabilised and retrieved. The
electrodynamic effects of moving such a tether through the
Earth's magnetic field will also be studied. The system also
houses 12 scientific experiments.
The tethered satellite was originally flown in 1992. Because of repeated problems with the deployment mechanism, the satellite could only be partially deployed and the experiment had to be interrupted. The equipment has now been modified.
There are many potential uses for tether systems. In the future, they could be used to generate electrical power for orbiting spacecraft, including the International Space Station, or for spacecraft propulsion. They could also be used for a range of atmospheric and aero-thermodynamic investigations through long-period exploration of the Earth's outer atmosphere.
Three Europeans on board
The two ESA astronauts
will participate as mission specialists. Claude Nicollier, from
Switzerland, will be making his third flight. He will be involved
in the dynamic phases of tether deployment and retrieval; he will
be the satellite 'navigator', closely monitoring its position and
movement. Nicollier was a mission specialist on the first TSS
flight, on board STS-46 in August 1992, during which ESA's
retrievable platform Eureca was also released. During his second
flight, STS-61 in December 1993, Nicollier operated the remote
arm during the refurbishment of the Hubble Space Telescope.
The second ESA astronaut, Maurizio Cheli, from Italy, will be making his first flight. He will perform the role of flight engineer and will control the extending of the boom to position the satellite for release.
A third European will be part of the seven-member crew. Umberto Guidoni, also from Italy, will fly as the TSS payload specialist. He will represent the Italian Space Agency (ASI). The other four members of the crew will be NASA astronauts.
Following the successful completion of the flight readiness review of the Ariane-5 launcher on 19 and 20 February, the review steering committee gave its approval for the start of the launch campaign, during which the launcher is readied for flight, on 4 March. The target date for the first launch of Ariane-5 has been set at 15 May.
The first qualification test of the cryotechnic stage was performed successfully in December at the launch site in Kourou, French Guiana. It lasted 10 minutes and 29 seconds, demonstrating the actual flight time of that stage. The second and last test was performed on 6 January. It lasted 9 minutes and 53 seconds. Both were carried out by CNES teams under the responsibility of Aérospatiale, the stage authority.
The other elements of the launcher, including the solid booster stages, storable propellant stage, fairing, Speltra, and vehicle equipment bay, have already been qualified. They were shipped to Kourou in mid-February (with the exception of the solid booster stages which are manufactured in Guiana).
ESA has delegated the management of its Ariane-5 programme to CNES, the French space agency.
New control centre opened
In preparation for the
Ariane-5 flights, a new launch control operations centre has been
built at the Guiana Space Centre. It features state-of-the-art
technology for spacecraft tracking, data transmission and
internal communications. It is already being used for Ariane-4
launches.
Following eight months of calibration and validation, the Global Ozone Monitoring Experiment (GOME) on board ESA's ERS-2 satellite is now beginning to deliver data that will enable valuable ozone monitoring. Although the ozone hole has been observed from space for nearly 10 years, it is only possible now to measure the trace gases that cause the ozone values to fluctuate.
Professor Paul Crutzen, Director of the Max Planck Institute for Chemistry in Mainz, Germany, and a winner of the 1995 Nobel Prize for Chemistry, recently presented some of the first calibrated and validated GOME data. Although it is still early in the mission, a group of researchers has already found one of the most 'hunted' trace gases, bromine oxide, in ERS-2 spectra, and another group has detected chlorine dioxide. Both are thought to affect ozone values.
The addition of GOME to ERS-2 is the major improvement that distinguishes it from its predecessor, ERS-1. ERS-2, launched in April 1995, is currently operating in tandem with ERS-1, launched four years earlier. As ERS-2 circles the Earth, GOME measures the intensity of the 'Earthshine' light over a large spectral range and at high resolution. Previous instruments have had 6 to 12 spectral channels, GOME has 3500, providing scientists with a very powerful tool for observing many rare atmospheric gases. Previously, such trace gases could only be measured from stratospheric balloons.
Prof. Paul Crutzen
ESA Bulletin Nr. 85.