Washington, May 22: On its way to deploy five Iridium Next communications satellites on Tuesday, a SpaceX Falcon 9 rocket will also launch twin NASA satellites that will monitor Earth's water cycle, marking a unique rideshare arrangement.

The satellites are scheduled to launch at 3.47 p.m. EDT from Vandenberg Air Force Base in Central California. (This corresponds to 1.17 a.m. Wednesday India time), NASA said. 

The two Gravity Recovery and Climate Experiment Follow-On mission (GRACE-FO) spacecraft will follow each other in orbit around Earth, separated by about 220 km.

On liftoff, the Falcon 9 first-stage engines will burn for approximately two minutes and 45 seconds before shutting down at main engine cutoff (MECO). 

The Falcon 9's first and second stages will separate seconds later. Then, the second-stage engine will ignite for the first time (SES1) and burn until the vehicle reaches the altitude of the injection orbit, 490 km.

While this burn is going on, the payload fairing -- the launch vehicle's nose cone -- will separate into two halves like a clamshell and fall away.

When the rocket's second stage has completed its ascent to the injection orbit altitude, it will pitch down (its nose points down) 30 degrees and roll so that one of the twin GRACE-FO satellites is facing down, toward Earth, and the other is facing up, toward space. 

Then the second stage engine will cut off (SECO).

About 10 minutes after liftoff, a separation system on the second stage will deploy the GRACE-FO satellites. 

Separation will occur over the Pacific Ocean at about 17.5 degrees North latitude, 122.6 degrees West longitude. 

The first opportunity to receive data from the spacecraft will occur at NASA's tracking station at McMurdo, Antarctica, about 23 minutes after separation, NASA said. 

After the GRACE-FO satellites are deployed, the Falcon 9 second stage will coast for half an orbit before reigniting its engine (SES2) to take the Iridium Next satellites to a higher orbit for deployment.

GRACE-FO, a collaborative mission of NASA and the German Research Centre for Geosciences (GFZ), continues the work of the original GRACE mission in observing the movement of water and other mass around our planet by tracking the changing pull of gravity very precisely.

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Batumi (Georgia), Jul 26 (PTI): Young Indian International Master Divya Deshmukh held her nerves to hold stalwart Koneru Humpy to a draw in game 1 of the FIDE Women's World Cup final, with both players having their share of opportunities to take the lead here on Saturday.

The draw with black means Humpy, the two-time World Rapid champion, holds a slight edge going in the second and final game under the classical chess rules in the two-game mini-match, and should the deadlock continue, games of shorter duration will be played to determine the winner.

Humpy employed the Queen's gambit accepted as black and it turned out to be a pretty fascinating game right out of the opening as Divya, 19, came up with a piece sacrifice early to deny the black king the right to castle.

Humpy was the first to err and, according to computers, Divya had things under control on the 14th move. However in her bid to recover the extra material, the Nagpur girl, who has secured a place in the Candidates tournament with her sterling performance here, missed a promising continuation.

What followed the exchange of all minor pieces and the ensuing queen and rook endgame gave enough counter play to both players. The game was eventually drawn after Humpy sacrificed her rook to force perpetual checks.

"The game saw an extremely sharp battle with the game ending in a draw in 41 moves. On move 7, Divya made her aggressive intentions clear by offering another pawn,

which looked like home preparation. Humpy made a practical decision of refraining from taking the pawn and a balanced position was reached by move 10 by white," said Grandmaster Pravin Thipsay, an Arjuna awardee and the first Indian to get a chess Grandmaster norm.

"However, instead of developing the undeveloped Knight, Humpy retreated the centralised Knight on move 10, giving huge positional advantage to Divya. Divya could have gained huge positional advantage on the 12th move by moving a rook. However, she chose to play for King side attack by sacrificing a piece instead.

"Humpy, too, erred at this stage and instead of moving the King to Queen side, moved it to the King side. Divya, on move 14, could have obtained a crushing attack by threatening a mate by developing her Queen. Instead she chose to exchange a pair of Bishops first, which enabled Humpy to defend her King by returning the piece," said Thipsay.

"Players thus reached a balanced Queen and two Rooks ending. Divya continued to play ambitiously and tried to attack Humpy’s King but the latter defended accurately and the game was drawn in 41 moves by perpetual check," he added.

In the play-off for the third place, Chinese players Zhongyi Tan, the former women's world champion and top seed Lei Tingjie also decided to split points out of a Queen’s gambit declined game.

The opening raised visions of a close contest between the two but having been knocked out of title race in the previous round, none of them wanted to take any huge risk. It was still a middle game when the players shook hands.

With the top two positions sealed for the Indians, the berth to the next Candidates is also assigned, while the player finishing third will also get an entry to the premier event scheduled for 2026.

Results: Divya Deshmukh (Ind) drew with Koneru Humpy (Ind); Zhongyi Tan (Chn) drew with Tingjie Lei (Chn).