Simplify the following text for a Grade 10 native English-speaking person.
Original: An occultation of Bamberga was observed on 8 December 1987 , and gave a diameter of about 228 km , in agreement with IRAS results .
Simplified: An occultation of Bamberga was seen on 8 December , 1987 , and gave a diameter of about 228 km , in agreement with IRAS results .