The announcement of a share repurchase program is generally seen as a positive signal by the market, indicating that the company believes its stock is undervalued. This can lead to an increase in stock price as the buyback reduces the number of shares outstanding, potentially increasing earnings per share. The significant size of the buyback ($500 million) and the increase in total authorization to $1.5 billion suggest strong confidence from Iridium's management in the company's future performance.