* Facebook shares down as expenses seen rising
* Orbital Sciences falls after rocket explosion
* Futures down: Dow 9 pts, S&P 3 pts, Nasdaq 10.5 pts
NEW YORK, Oct 29 (Reuters) - U.S. stock index futures dipped on Wednesday, weighed by a sharp decline in Facebook Inc shares and ahead of a statement from the U.S. Federal Reserve as it winds down its stimulus program.
* In an otherwise data-light session, the Fed is likely to announce that it will no longer add to its holdings of Treasury bonds and mortgage-backed securities, effectively ending a program that at its peak pumped $85 billion a month into the financial system.
* The Fed's cash injection is widely seen as a pillar of the current multiyear bull market in equities, and earnings are expected to support any further advances. So far this reporting season, 73.5 percent of S&P 500 companies have beat profit expectations. In a typical quarter since 1994, 63 percent of companies beat estimates.
* Facebook shares fell 7.7 percent in premarket trading the day after the social network announced an increase in spending in 2015 and projected a slowdown in revenue growth this quarter.
* Orbital Sciences Corp shares fell 13.7 percent in light volume the day after its unmanned rocket exploded seconds after liftoff from a commercial launch pad in Virginia, marking the first accident since NASA turned to private operators to deliver cargo to the International Space Station.
Futures snapshot at 07:19 EDT (1119 GMT):
* S&P 500 e-minis were falling 3.25 points, or 0.16 percent, with 130,394 contracts changing hands.
* Nasdaq 100 e-minis were down 10.5 points, or 0.26 percent, in volume of 25,600 contracts.
* Dow e-minis were down 9 points, or 0.05 percent, with 16,783 contracts changing hands. (Reporting by Rodrigo Campos)