By Noel Randewich

June 26 (Reuters) - Shares of SpaceX rose a marginal 0.15% on Friday ahead of its inclusion in Russell indexes, with passively managed funds tracking those benchmarks required to add billions of dollars' worth of Elon Musk's internet and rocket company to their holdings.

Traders exchanged about $19 billion worth of SpaceX shares, with almost half of that turnover in the final minutes of the session.

After a blockbuster initial public offering this month, SpaceX's stock has been on a wild ride, soaring 67% to its June 16 intraday high of $225.64 before tumbling to Friday's $153.23 close.

The stock remains well above the $135 IPO price as investors assess how to value a company that lost $4.9 billion last year, but that backers expect to dominate the satellite internet, AI and commercial space launch markets that they believe will define the next decade of global infrastructure. FTSE Russell is adding SpaceX to its Russell U.S. indexes after Friday's close of trading as part of its semi-annual index reconstitution. That means passively managed exchange-traded funds that track Russell indexes, such as the iShares Russell 1000 ETF, must add SpaceX shares to their portfolios before Monday's session.

When new companies are added to an index, passively managed funds adjust their holdings while trying to minimize the "tracking error" between their funds' performance and the index that can result if their buy-in price differs from the closing price.

While SpaceX's $2 trillion market capitalization makes it almost as valuable as Amazon(AMZN), only about $100 billion of shares have been listed for trading on the stock market, with the rest owned by Musk, other insiders and employees.

Passively managed funds need to buy over $4 billion worth of SpaceX shares to match the Russell indexes they track, according to a report on Friday from Melissa Roberts, a quantitative analyst at Stephens.

SpaceX is also eligible to be added to the tech-heavy Nasdaq 100 on July 6, an event that will force large index funds such as the Invesco QQQ ETF, which tracks that index, to buy its shares.

Following losses in recent sessions, SpaceX is trading at around 107 times its 2025 sales, an astronomical valuation. By comparison, AI heavyweight chipmaker Nvidia(NVDA) recently traded at 21 times sales. S&P Global blocked SpaceX from joining the S&P 500 index after it said this month it would not change its inclusion criteria to accommodate megacap IPOs. To ​be included in the S&P 500, a company must be profitable in its most recent quarter as ​well as for the sum of its most recent four quarters, according to one of the rules S&P left unchanged.

(Reporting by Noel Randewich in San Francisco and Saqib Iqbal Ahmed in New York; editing by Colin Barr, Rod Nickel)