First reports of ISS sightings since the addition of the new solar panels indicate the brightness is little changed! Addition of new solar panels Several people have requested information on the brightness of the ISS and how it will change with the addition of the new solar arrays during Shuttle mission STS-97. We are not making any adjustments yet to the brightness predictions at Heavens-Above, simply because we can't be sure what effect the new panels will have. Many people have automatically assumed that they will make the ISS appear much brighter, but this isn't necessarily the case. The new panels certainly have a huge area, but they will be oriented towards the Sun to maximise the energy generated, and most of the light will be reflected back towards the Sun and not in the direction of observers on the ground. The panels will actually cast large shadows on the rest of the ISS and it's even possible the brightness will be slightly less! There are just too many unknowns to be sure, so we prefer to "wait and see", and will adjust the brightness predictions after the panels are installed and the Shuttle is undocked. Don't forget that the Shuttle itself adds significantly to the brightness when it visits the ISS. Most satellite magnitude estimates are based on observations since they are very difficult to calculate using theory alone. Although the new panels might not increase the brightness, one can safely say that the ISS will generally become brighter as new modules are added over the coming months and years. As a rough guess, it might reach magnitude -3 at its best, which is much brighter than Mir and Sirius, the brightest star in the sky at magnitude -1.4. Will the ISS produce flares ? This is another frequently asked question, and the simple answer is that, yes, the ISS will almost certainly produce very bright flares, as do many other satellites including Mir. The problem is that they are not predictable because the attitude of the ISS is not as tightly controlled as that of the Iridium satellites, so just keep looking and you might be lucky.

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