Why Was It Difficult to Predict When and Where Tiangong-1 Will Drop to Earth?


The Chinese space station Tiangong-1 finally landed on Earth’s surface. But over the past few weeks, there was much anticipation and worry over where the space debris will fall. For two years, Tiangong-1 finally finished the process of tumbling back down to the planet. Over the past months, those on the ground have no idea the exact time and place that the space debris will fall down.

Uncertainty over Tiangong-1’s Drop

There were over 10 space stations working together to find out when and where it will drop. However, even with all the resources they have, the best they can conclude is it will fall somewhere between 43 degrees N and 43 degrees South. The tricky part is this location encompasses most of Earth so it did not really help. Not that it matters now when Tiangong-1 safely fell down.

However, some people still wonder why it was so difficult to predict the exact time and location of Tiangong-1’s descent. Why was there so much uncertainty when already so many space stations were working together in anticipation of it? The key, apparently, is the extremely quick movement of the space station while it gradually falls.

Unpredictable Nature of Atmosphere and Tiangong-1’s Orientation

Add to that, the atmosphere’s unpredictable nature significantly increased the difficulty of predicting the descent of Tiangong-1. On that note, the estimated timing of Tiangong-1’s plunge to Earth moved a little later in just an overnight on March 31. It moved to a little later on April 2, with the location still an uncertainty.

The change for the timeframe is said to be a quiet solar activity. As it turns out, the solar flares, as well as coronal mass ejections of an active sun, had an effect on Tiangong-1’s plunge. The gases in Earth’s atmosphere absorb low wavelengths of the electrically charged matter from the sun. This results in the upper atmosphere’s increased density.

Because of the increased density, there is more drag when the space lab hurtles down the Earth’s atmosphere that keeps it aloft. This was supposed to slow down the approach of the space station. However, the expected solar flare did not arrive and that is why its expected descent changed. In addition to this, its orientation as it fell into the atmosphere is also a factor.

These are the two main factors that influence the descent of space debris’ descent to Earth. With hundreds of thousands of other space junks circling above the planet, it is great to know about the difficulty of predicting their plunge.