So many things going on there in Space… I’m indicating the points only..
On September 7, 2011, NASA announced the impending uncontrolled re-entry of UARS and noted that there is a small risk to the public. As of September 21, 2011, the orbit of UARS was 195 km (121 mi) by 210 km (130 mi). Re-entry is projected for 23 September 2011. Some debris may survive to reach the surface. Of the 26 pieces expected to survive reentry and strike the surface, the largest piece is expected to have a mass of 158.3 kg (349 pounds), and to reach the surface at a velocity of 44 meters/second (98 miles/hour). Smaller pieces are expected to strike the surface at up to 107 meters/second (239 miles/hour). >>>Wiki
There is nothing really to worry about..As there is a very small chance for the debris to hit your head. 
OK that’s all about the UARS, now we come to the biggest threat>>
The EleNin X
It’s sounds strange as the word itself remembers me with Nine Eleven
I Call it the EleNin X, as I’m not sure if it is a Comet, Brown dwarf , Nibiru or Planet X..Whatever
WHAT WILL HAPPEN AND WHEN?
on 26th September 2011 as people say..
yep, few days to go from the date of this post.
I’ll leave you with the videos below..have a look at it and give me your thoughts..
Click here for short video in Arabic subtitle Part 1 , Part 2.
I believe in Allah (God)..No one knows when the doomsday will occur.
بِسۡمِ ٱللهِ ٱلرَّحۡمَـٰنِ ٱلرَّحِيمِ
يَسۡـَٔلُونَكَ عَنِ ٱلسَّاعَةِ أَيَّانَ مُرۡسَٮٰهَاۖ قُلۡ إِنَّمَا عِلۡمُهَا عِندَ رَبِّىۖ لَا يُجَلِّيہَا لِوَقۡتِہَآ إِلَّا هُوَۚ ثَقُلَتۡ فِى ٱلسَّمَـٰوَٲتِ وَٱلۡأَرۡضِۚ لَا تَأۡتِيكُمۡ إِلَّا بَغۡتَةً۬ۗ يَسۡـَٔلُونَكَ كَأَنَّكَ حَفِىٌّ عَنۡہَاۖ قُلۡ إِنَّمَا عِلۡمُهَا عِندَ ٱللَّهِ وَلَـٰكِنَّ أَڪۡثَرَ ٱلنَّاسِ لَا يَعۡلَمُونَ (١٨٧)
In the name of Allah, the Beneficent, the Merciful
They ask you about the Hour (i.e. the Doomsday), “When is it due to happen?” Say, “Its knowledge is only with my Lord. No one can unfold it except He at its time. It shall weigh heavy in the heavens and the earth. It shall not come upon you but suddenly.” They ask you as if you were aware of it. Say, “Its knowledge is only with Allah, but most of the people do not know.” (187) The Holy Qur’an
Surah Al-Araf – سُوۡرَةُ الاٴعرَاف
At the end, EleNin X which is most probably to be a comet, wont harm the planet.. Lets wait and time will tell 
Please have a look at my old previous post: December 21 2012