Concerns over related events such as North Korea's recent salvo of ballistic missile tests, and North Korea's apparent preparations for a nuclear test were mentioned occasionally, but the world seems to have let this rather interesting event slip by unnoticed.

A rocket launch is normally hard to conceal, but if you logged onto the JAXA (Japan Space Exploration Agency) Web cam for its Tanegashima launch site on launch day, you would have been greeted by an interesting view. This camera normally points at the latest rocket on the pad, but for some reason, in the hours prior to the latest satellite launch, the rocket and its launchpad were nowhere to be seen!

The camera had been pointed elsewhere, giving viewers a pleasant ocean view that was devoid of anything sensitive. Never mind that pictures of the latest H2-A launch made their way into the media soon after the rocket thundered aloft. JAXA can stage a major launch and simply pretend it does not exist.

Their Web site barely acknowledged the mission before launch (you had to dig through several pages to find it on a launch schedule), and failed to report it as news afterwards. Admittedly, this was not a JAXA spacecraft, but the agency could at least have acknowledged a flight that used its launch vehicle and facilities.

We have been told very little about this latest satellite, except for the fact that it is an optical satellite with a fairly high resolution. If the reports are true, this was also a single satellite launch. Contrast this with Japan's two previous spy satellite launches, which were both tandem affairs.

On each previous flight, one satellite carried an optical scanner, while the second was a radar imaging satellite. The first launch, in March 2003, was successful, but Japan's second attempt in November of that year ended in a launch failure.

No photos or diagrams of this satellite have been released, but can we make an educated guess about its appearance?

A single satellite on this rather powerful rocket suggests that this bird is fairly large. It is possible that Japan has elected to reuse the bus that was flown for its ALOS (Advanced Land Observation Satellite) mission. This was an Earth Observation mission, albeit with a different array of sensors. It makes sense to use a proven platform to save time and development costs, especially when the mission is somewhat strategically urgent.

We could assume that the large synthetic aperture radar panel used on ALOS wouldn't have flown on the latest IGS. If Japan wants a military-grade radar observation system, it will fly on a dedicated satellite platform. Japan has indicated that another satellite launch, scheduled for later this year, will carry such a payload.

The absence of radar on the latest satellite would decrease the need for the huge solar panel carried by ALOS, so we can cut down on the size of the panel on our hypothetical IGS. This will still provide enough power for the mission, but save weight. Similarly, the scanners and sensors used for environmental monitoring would be removed.

This loss in weight is backed up by the use of a lightweight version of the H2-A launch vehicle, which did not use the same configuration of boosters as other missions.

In place of the ALOS sensor array in the front of the bus, we would place the IGS imagery package. A high resolution suggests a telescope-type camera system has been used, instead of the scanner array used on ALOS and possibly the first-generation optical IGS.

The camera would be mounted on a package containing support electronics and probably some form of mechanical vibration dampener, to prevent minor jostles from the satellite bus from ruining image definition. This package could also allow the camera to be slewed at different angles, permitting a wider ground track to be covered. Alternatively, the slew option could be done with a mirror, periscope-style, placed in front of the optical system.

ALOS carried its solar panel on the opposite side of the satellite to the large radar array, for balance reasons, and also to keep it away from most of the instruments. The loss of the radar suggests that the solar panel itself should be moved. Smaller panels are typically now placed at the rear of satellite buses like car spoiler fins, as seen in the French SPOT satellites.

With these factors in mind, I have produced a crude impression of what Japan's latest Information Gathering Satellite could look like. In the absence of any official data or speculative drawings, this is an attempt to fill an information vacuum. Soon, amateur astronomers will probably provide more clues to the appearance of this satellite through actual photography of the bird in orbit. What else will will find out? It's watching us. We can watch it too.

Dr Morris Jones is a lecturer at Deakin University, Australia

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