Sirius Satellite Radio and merger partner XM Satellite Radio announced their future plans to raise more capital, a move which caused shares to drop on Monday trading.

The news of the new plans came as Sirius made public the preliminary results for its second quarter early Monday. The company said it anticipates a 25% jump in both revenue and subscriber numbers compared to a year ago.

Satellite radio pioneer Sirius made clear its plans to sell about $375 million in common stock in a fixed-price public offering and another $65 million to come later concurrently with a private offering by XM. The company did not say how many shares it will offer, but it will surely depend on the terms of the XM offering.

XM Satellite Radio Holdings said it will offer $550 million of senior notes, due in 2014, and exchangeable into shares of Sirius common stock.

Sirius stock dropped 37 cents, or 16.4%, to $1.88, while XM fell $1.11, or 11.9%, to $8.17.

According to a company statement, Sirius estimated second quarter revenue to be of approximately $283 million, up from $226 million in the same period in 2007. Its subscriber count rose 25% from a year earlier to 8.92 million.