The shuttle Discovery's crew will attempt to activate the ship's suspect Ku-band radar during the final stages of rendezvous with the International Space Station early Wednesday. But if it doesn't work - and engineers don't believe it will - the astronauts will use other sensors to update the shuttle's navigation systems.

Credit: NASA TV

"We will execute the rendezvous and docking operations per the crew's radar-failed procedures," said LeRoy Cain, chairman of NASA's Mission Management Team. "Those procedures ... are practiced and trained as part of their normal training template."

Other than the post-launch loss of the shuttle's Ku-band communications system due to an unknown failure, Cain said Discovery appeared to come through its climb to space Monday in generally good condition. But engineers are studying photographs that appear to show a tile, or some similar-sized object, separating from the left side of the shuttle's vertical tail fin 42.2 seconds after liftoff as the ship was accelerating through Mach 1.

Cain wouldn't speculate on what the object might have been, although the imagery suggests it likely was a heat shield tile from the left side of the rudder-speedbrake's trailing edge.

"Preliminarily, I don't believe this will be any impact to us," he said. "Those tiles are in place primarily for ascent heating, the thermal environment back there with the engines running. For entry, the speedbrake is, of course, clamped closed like it is for ascent through the entire max heating portion of the entry profile and it's in the aerodynamic shadow during that entire time. Then the speedbrake opens at Mach 10.

"This is going to turn out to be a non issue for us, is what I expect," he said. "But we want the team to go off and do their normal, rigorous analysis and assessment of it."

Video cameras captured object flying away from the shuttle's tail. Credit: NASA TV

The only other issue of any significance is the failure of Discovery's Ku-band dish antenna, used to send and receive data, commands, voice traffic and video, following launch Monday. While the antenna can track NASA's communications satellites, the two electronic subsystems that transmit and receive data appear to have suffered some sort of common failure.

One of those subsystems turns the antenna into a radar for use during rendezvous operations. The astronauts have not yet attempted to activate the radar subsystem but given the antenna's other problems, engineers are not optimistic.

But Cain said the presumed loss of the Ku in radar mode will not have a major impact on the crew's ability to rendezvous with the space station.

"We have a whole suite of navigation and rendezvous sensors that we use normally in addition to the Ku radar," he said. "In this case, we'll use those exclusively, to include the star trackers that we use for navigation, the handheld lasers as well as the trajectory control system, or TCS. So all of those systems are available and we don't anticipate any issues whatsoever with performing the radar-failed procedures for the rendezvous."

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Trailing the space station by about 9.2 miles, commander Alan Poindexter and pilot James Dutton will begin the terminal phase of the rendezvous procedure at 1:06 a.m. EDT Wednesday with a critical rocket firing. As with all post-Columbia station flights, Poindexter will position the shuttle directly below the station and then perform a back-flip maneuver, starting around 2:43 a.m., to expose the ship's belly to the station.

Expedition 23 commander Oleg Kotov and flight engineer Timothy Creamer, using digital cameras with 400-mm and 800-mm lenses, will photograph the shuttle's heat shield from the station and downlink the images to mission control for analysis.

Poindexter then will guide Discovery to a point about 300 feet directly in front of the station before moving in for a docking at the lab's forward port around 3:44 a.m.

One of the first items on the agenda will be to connect to the station's wireless computer network so the shuttle crew can downlink about 40 gigabytes of data collected during an inspection of Discovery's nose cap and wing leading edge panels early Tuesday. That data normally is downlinked in realtime, but the failure of the Ku-band antenna has forced the crew to rely on the station's communications system.

"All of that data we've loaded onto one of the computers on board the shuttle and once we get docked, we'll transfer that data to the station laptop computer system and we'll do that via the wireless network we normally have configured for these shuttle-station docked missions," Cain said.

"That data will all be on the ground by about 11 o'clock local time tomorrow. Then the Damage Assessment Team will be able to review all that data as they normally do and they'll be able to give us a good idea, by the time we get to the MMT tomorrow, very preliminarily, if we have anything to be concerned about."

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision A of the NASA television schedule):

EDT........DD...HH...MM...SS...EVENT

04/06
08:21 PM...01...14...00...00...STS/ISS crew wakeup (begin flight day 3)
09:16 PM...01...14...55...00...ISS daily planning conference
09:51 PM...01...15...30...00...Group B computer powerup
10:06 PM...01...15...45...00...Rendezvous timeline begins
11:31 PM...01...17...10...00...Spacesuit removal from airlock
11:34 PM...01...17...13...26...NC-4 rendezvous rocket firing

04/07
01:06 AM...01...18...45...19...Ti burn; range = 9.2 miles
01:45 AM...01...19...23...54...Sunset
02:05 AM...01...19...43...55...Range = 10,000 ft
02:14 AM...01...19...52...35...Range = 5,000 ft
02:19 AM...01...19...58...04...Range = 3,000 ft
02:20 AM...01...19...59...09...Sunrise
02:23 AM...01...20...02...13...MC4
02:27 AM...01...20...06...13...Range = 1,500 ft
02:32 AM...01...20...11...13...Range = 1,000 ft
02:32 AM...01...20...11...18...RPM Start Window Open
02:35 AM...01...20...14...13...KU to LO (800 ft)
02:36 AM...01...20...15...13...Shuttle below ISS (725 ft)
02:41 AM...01...20...20...25...Range = 600 ft
02:43 AM...01...20...22...19...Start Pitch Maneuver
02:48 AM...01...20...27...16...Noon
02:51 AM...01...20...30...19...End Pitch Maneuver
02:54 AM...01...20...32...55...Initiate TORVA (575 ft)
02:56 AM...01...20...35...14...RPM Full Photo Window Close
03:05 AM...01...20...43...39...RPM Start Window Close
03:05 AM...01...20...44...25...Shuttle in front of ISS (310 ft)
03:06 AM...01...20...45...15...Range = 300 ft
03:10 AM...01...20...49...25...Range = 250 ft
03:15 AM...01...20...53...35...Range = 200 ft
03:16 AM...01...20...55...23...Sunset
03:17 AM...01...20...56...05...Range = 170 ft
12:19 PM...01...29...57...45...Range = 150 ft
03:23 AM...01...21...01...55...Range = 100 ft
03:26 AM...01...21...04...55...Range = 75 ft
03:30 AM...01...21...09...05...Range = 50 ft
03:33 AM...01...21...12...25...Range (30 ft) Station Keeping Start
03:38 AM...01...21...17...25...Push to Dock
03:43 AM...01...21...21...45...Range = 10 ft

03:44 AM...01...21...23...26...DOCKING

03:52 AM...01...21...30...40...Sunrise
04:11 AM...01...21...50...00...Leak checks
04:46 AM...01...22...25...00...Orbiter docking system prepped for ingress
04:41 AM...01...22...20...00...Group B computer powerdown
05:11 AM...01...22...50...00...Hatch open
05:41 AM...01...23...20...00...Welcome aboard!
05:56 AM...01...23...35...00...Safety briefing
06:31 AM...02...00...10...00...Spacesuits moved to Quest
06:31 AM...02...00...10...00...SRMS OBSS handoff
08:01 AM...02...01...40...00...REBA checkout
09:36 AM...02...03...15...00...ISS evening planning conference
11:51 AM...02...05...30...00...ISS crew sleep begins
12:21 PM...02...06...00...00...STS crew sleep begins

Additional coverage for subscribers:
VIDEO: PREVIEW OF RENDEZVOUS AND DOCKING ACTIVITIES PLAY
VIDEO: OBJECT LOST FROM SHUTTLE TAIL DURING LAUNCH PLAY
VIDEO: TUESDAY AFTERNOON'S MANAGEMENT TEAM UPDATE PLAY
VIDEO: THE FULL STS-131 LAUNCH EXPERIENCE PLAY

VIDEO: FLIGHT DAY 2 HIGHLIGHTS MOVIE PLAY
VIDEO: TUESDAY MORNING'S MISSION STATUS BRIEFING PLAY
VIDEO: PREVIEW OF FLIGHT DAY 2 ACTIVITIES PLAY
VIDEO: NARRATED TOUR OF DISCOVERY'S PAYLOAD BAY PLAY
VIDEO: DESCRIPTION OF KU-BAND ANTENNA PROBLEM PLAY

VIDEO: FLIGHT DAY 1 HIGHLIGHTS MOVIE PLAY
VIDEO: SHUTTLE DISCOVERY BLASTS OFF! PLAY | HI-DEF
VIDEO: GO INSIDE MISSION CONTROL DURING LAUNCH PLAY
VIDEO: POST-LAUNCH NEWS CONFERENCE PLAY

VIDEO: LAUNCH REPLAY: VAB ROOF PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PRESS SITE PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PATRICK AFB PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD PERIMETER PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: BEACH TRACKER PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD CAMERA 070 PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD CAMERA 071 PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PLAYALINDA BEACH PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD FRONT CAMERA PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: KSC WEST TOWER PLAY | HI-DEF

VIDEO: ASTRONAUTS LEAVE CREW QUARTERS PLAY | HI-DEF
VIDEO: CREW FINISHES GETTING SUITED UP PLAY | HI-DEF

VIDEO: NARRATED REVIEW OF SHUTTLE'S PREPARATIONS PLAY | HI-DEF
VIDEO: NARRATED REVIEW OF PAYLOADS' PREPARATIONS PLAY | HI-DEF
VIDEO: PREPARING AN EXTERNAL TANK FOR LAUNCH PLAY | HI-DEF

VIDEO: TIME-LAPSE OF GANTRY ROLLING BACK FOR LAUNCH PLAY
VIDEO: LAUNCH PAD'S SERVICE TOWER RETRACTED PLAY | HI-DEF
VIDEO: PAYLOAD BAY DOORS CLOSED FOR LAUNCH PLAY | HI-DEF
VIDEO: ASTRONAUTS INSPECT THE PAYLOAD BAY PLAY | HI-DEF

VIDEO: STS-131 MISSION PREVIEW MOVIE PLAY | HI-DEF
VIDEO: PRE-LAUNCH INTERVIEW WITH COMMANDER POINDEXTER PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH PILOT JIM DUTTON PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH RICK MASTRACCHIOPLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH METCALF-LINDENBURGER PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH STEPHANIE WILSON PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH NAOKO YAMAZAKI PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH CLAY ANDERSON PLAY

VIDEO: PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: COUNTDOWN STATUS AND WEATHER OUTLOOK PLAY
VIDEO: PREVIEW OF DISCOVERY'S LAUNCH COUNTDOWN PLAY
VIDEO: ASTRONAUTS ARRIVE FOR LAUNCH PLAY | HI-DEF

VIDEO: FULL FLIGHT READINESS REVIEW NEWS BRIEFING PLAY
VIDEO: RECAP OF THE FLIGHT READINESS REVIEW PLAY | HI-DEF
VIDEO: HELIUM VALVE NO CONSTRAINT TO LAUNCH PLAY | HI-DEF
VIDEO: MANAGERS ASSESS ISSUES BEFORE FLIGHT PLAY | HI-DEF
VIDEO: UPDATE ON PRE-LAUNCH PREPS AT PAD 39A PLAY | HI-DEF

VIDEO: SPACEWALKING SUITS LOADED ABOARD PLAY | HI-DEF
VIDEO: INTERVIEW WITH STS-131 PAYLOAD MANAGER PLAY | HI-DEF
VIDEO: INTERVIEW WITH BOEING PAYLOAD MANAGER PLAY | HI-DEF
VIDEO: PAYLOADS DELIVERED TO LAUNCH PAD 39A PLAY | HI-DEF
VIDEO: TRANSPORT CANISTER ROTATED VERTICALLY PLAY | HI-DEF
VIDEO: LEONARDO PLACED INTO THE TRANSPORTER PLAY | HI-DEF
VIDEO: STATION'S NEW AMMONIA COOLANT TANK PLAY | HI-DEF
VIDEO: LEONARDO HATCH CLOSED FOR FLIGHT PLAY | HI-DEF
VIDEO: FILLING UP ONE OF THE SUPPLY RACKS PLAY | HI-DEF

VIDEO: CAN THE SHUTTLE PROGRAM AVOID LOOMING RETIREMENT? PLAY
VIDEO: WHAT ABOUT ADDING ONE MORE SHUTTLE MISSION? PLAY
VIDEO: FULL BRIEFING BY SHUTTLE AND STATION OFFICIALS PLAY
VIDEO: THE STS-131 MISSION OVERVIEW PRESENTATIONS PLAY
VIDEO: PREVIEW BRIEFING ON MISSION'S SPACEWALKS PLAY
VIDEO: THE ASTRONAUTS' PRE-FLIGHT NEWS BRIEFING PLAY

VIDEO: SHUTTLE EVACUATION PRACTICE PLAY | HI-DEF
VIDEO: CREW MODULE HATCH IS CLOSED PLAY | HI-DEF
VIDEO: ASTRONAUTS BOARD DISCOVERY PLAY | HI-DEF
VIDEO: CREW BRIEFED ON EMERGENCY PROCEDURES PLAY | HI-DEF
VIDEO: TEST-DRIVING AN EMERGENCY ARMORED TANK PLAY | HI-DEF
VIDEO: NIGHTTIME APPROACHES IN TRAINING AIRCRAFT PLAY | HI-DEF
VIDEO: ASTRONAUTS CHAT WITH REPORTERS AT PAD 39A PLAY
VIDEO: CREW ARRIVES FOR PRACTICE COUNTDOWN PLAY | HI-DEF

VIDEO: GANTRY PLACED AROUND DISCOVERY PLAY | HI-DEF
VIDEO: DISCOVERY REACHES PAD 39A PLAY | HI-DEF
VIDEO: OVERNIGHT ROLLOUT BEGINS PLAY | HI-DEF
VIDEO: SHUTTLE HOISTED FOR ATTACHMENT TO TANK PLAY | HI-DEF
VIDEO: CRANE ROTATES THE ORBITER VERTICALLY PLAY | HI-DEF
VIDEO: DISCOVERY MOVES TO ASSEMBLY BUILDING PLAY | HI-DEF

VIDEO: ASTRONAUTS VISIT THEIR SPACECRAFT PLAY | HI-DEF
VIDEO: CREW GOES INSIDE LEONARDO MODULE PLAY | HI-DEF

VIDEO: EXTERNAL TANK ATTACHED TO BOOSTERS PLAY | HI-DEF
VIDEO: FUEL TANK LIFTED INTO CHECKOUT CELL PLAY | HI-DEF
VIDEO: EXTERNAL TANK ARRIVES AT SPACEPORT PLAY | HI-DEF

VIDEO: DISCOVERY'S NOSE POD ATTACHED PLAY | HI-DEF
VIDEO: INSTALLING DISCOVERY'S MAIN ENGINES PLAY | HI-DEF
VIDEO: KSC'S SHUTTLE MAIN ENGINE SHOP PLAY | HI-DEF
VIDEO: GASEOUS NITROGEN TANK REMOVED PLAY | HI-DEF
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