Federal regulators have cleared the last remaining hurdle for Sirius Satellite Radio’s proposed acquisition of XM Satellite Radio Holdings, a deal that will combine rivals in the nascent U.S. pay-radio market.

The U.S. Federal Communications Commission reached an agreement to conditionally approve the deal on Thursday, four months after the Department of Justice gave its blessing, and 18 months after XM and Sirius agreed to combine. Experts say that new services from a combined company could come in a few months, but suggest their holiday subscription growth may be hurt by the delayed deal closing.

Here are are some important dates in the history of the satellite radio industry.

* 1994 - CD Radio goes public at about $3.15.

* Oct. 1999 - XM goes public at $12 a share.

* Nov. 1999 - CD Radio changes its name to Sirius Satellite.

* Nov. 2001 - XM starts national radio service, after launching its first two satellites — “Rock” and “Roll” — earlier in the year.

* 2002 - Sirius launches national satellite radio service.

* Oct 2003 - XM reaches 1 million subscribers.

* Dec 2003 - Sirius signs 7-year, $220 million pact with the National Football League.

* Oct 2004 - Shock Jocks Opie and Anthony begin broadcasting on XM, on a premium channel.

* Oct 2004 - XM signs 11-year, $650 million pact with Major League Baseball; deal starts with the 2005 season.

* Oct 2004 - XM unveils Delphi MyFi, its first portable radio receiver.

* Dec 2004 - Sirius reached 1 million subscribers

* Oct 2004 - Sirius signs shock jock Howard Stern to 5-year, $500 million deal.

* April 2005 - XM raises subscription price to $12.95 a month from $9.99, matching Sirius.

*Sept 2005 - XM surpasses 5 million subscribers.

* Feb 2006 - XM signs 3-year, $55 million deal with Oprah Winfrey.

* Sept 2006 - Sirius tops 5 million subscribers.

* Jan 2006 - Sirius starts broadcasts of Howard Stern.

* Feb 2007 - Sirius and XM propose merger; Deal requires approval of their respective shareholders, the U.S. Federal Communications Commission and the U.S. Justice Department. Sirius CEO Mel Karmazin to be CEO of new company, XM Chairman Gary Parson to become Chairman.

* July 2007 - CEO Hugh Panero says he is stepping down in August; COO Nate Davis to become Interim CEO.

* Nov 2007 - XM and Sirius shareholders approve the deal.

* Mar 2008 - The Justice Department approves the deal.

* June 16, 2008 - FCC Chairman Kevin Martin announced his recommendation to approve the merger with conditions.

* June 30, 2008 - Sirius ends the second quarter with 8.9 million subscribers, up 25 percent from a year earlier. XM had 9.65 million subscribers at the end of June, up 17 percent from a year earlier.

* July 25, 2008 - FCC Commissioners approve the deal with conditions, clearing the way for a deal that will leave just one U.S. satellite radio service. Analysts expect the deal to close within days or weeks of the regulatory approval.

(Sources: XM, Sirius, Hoover’s, Reuters)

(Top picture: A Russian Proton with a satellite for Sirius Satellite Radio is lifted into place at its launching pad at the Baikonur Cosmodrome, Kazakhstan, on September 1, 2000, while (L to R) Bob Prevaux, Program Director for Space Systems Loral talks with Rob Briskman, Executive Vice President for Sirius Satellite Radio and Ted Sitek, Mission Manager for International Launch Services. (Reuters/Karl Ronstrom))

Sirius Satellite Radio and XM Satelite Radio want the FCC to know that they are ready.

Like REALLY REALLY READY.

Sure, combined they racked up $230 million in losses in the first quarter. And they added 600,000 net subscribers, to make a combined total of over 17 million.

So what?

What everyone wants to know is when their proposed merger — you know the one announced back in the 1990s in February 2007 will finally close. After 15-months, the individual performance of each company, while important, takes a backseat to knowing when they can combine their efforts. Or,  should the deal fall apart, when they can go back to scratching and clawing for the next hot media property (like the “Dr. Phil Channel” or “The 24-hour World Series of Poker Channel.”)

Each company hosted 45-minutes-short conference calls and sent their respective CEOs up to the microphone to say, “We are Ready“, like the Father at a holiday feast proclaiming that the time has come to stop horsing around –he is about to carve the roast beast.

XM’s Nate Davis seemed to say, “You are great, but I hope this is goodbye.”

Let me just say while the process has clearly been a protracted one, we remain hopeful that we are nearing the end of the process and that this will be the last stand-alone quarterly earnings call we will have.

Sirius’ Mel Karmazin comments were a little more, shall we say, pointed.

This is our fifth quarterly conference call since we announced the merger and…

I share the sentiment I hear from many of you regarding the length of time it is taking to complete our transaction. It is almost 350 days on the FCC clock from when it was put on public notice. (Mediafile: He said the FCC usual mulling time is 180 days). We also share the outrage that some have expressed to me regarding press reports of opportunistic parties trying to take advantage of the process and extract value for themselves that properly belongs to Sirius subscribers and shareholders.

I am optimistic that we are getting close to the finish line and will be able to close the deal.

The only problem is, noone knows how close “close” is.

According to Cowen and Co. analyst Tom Watts, that could be, any day now… or not.

The next step toward an FCC approval will be an Order for Circulation issued by FCC Chairman Martin where he will circulate his recommendation and proposal to fellow Commissioners. While timing of this Order is uncertain, its importance implies that an FCC meeting is not necessary to approve the merger.

(Photo: XM CEO Nate Davis, XMRadio.com; Sirius CEO Karmazin, Reuters file)

A cottage industry has risen from the ashes of Eliot Spitzer’s career and, well, life. Echoing Jay-Z’s words, Client 9 “is no businessman…he’s a business, man.”

Ok, maybe not an industry in the traditional sense. But certain opportunists companies are at least looking to make a quick buck on the former “Wall Street Sheriff’s” woes. It didn’t take long for Virgin Mobile Canada and Sirius Satellite Radio to add their takes on Client 9, Spitzer’s infamous court document alias.

“When you call us we’ll treat you like a person, not a client. Whether you’re #9 or #900, you’ll get hooked up with somebody who’ll finally treat you just how you want to be treated,” Virgin Mobile Canada promised.

Sirius Satellite Radio went a step further by creating and promoting a weekend of programming billed as “Client 9 Radio.”

“Client 9 Radio will serve as a forum for this national conversation,” Sirius announced on Friday. “Client 9 Radio will explore every side of the story: from the political to the psychological to the medical and beyond.”

A representative of YouMail, a company that lets users save their voicemails, also chimed in: “With the recent developments regarding Eliot Spitzer being exposed through wiretaps, I can’t help but wonder when saved and easily shared voicemails will be used to uncover the next big business or political scandal.”

On Tuesday, a day after the New York Times first reported the Spitzer’s ties with a prostitute ring, vendors were already hawking T-shirts. “Client #9 for President, Help Legalize Prostitution” T-Shirts were available over at CafePress.

Client 9 even hit lunch, Gothamist reports. Eisenberg’s Sandwich Shop in New York started serving “The Spitzer” sandwich made with “hot tongue,” naturally.And apparently without even trying, News Corp earned publicity from the debacle in the form of reports about the MySpace page were “Kristen,” Spitzer’s alleged lady-friend shared her story and her music.

(Photos: Virgin Mobile Canada; Sirius Satellite Radio)