July 7, 1995

KSC RELEASE NO. 66-95

SPACE SHUTTLE MISSION STS-70 LAUNCH COUNTDOWN TO BEGIN MONDAY

	The countdown for launch of the Space Shuttle Discovery on
mission STS-70 is scheduled to begin Monday, July 10 at 10 a.m. EDT,
at the T-43 hour mark. The KSC launch team will conduct the countdown
from Firing Room 3 of the Launch Control Center.

	The countdown includes 28 hours and 41 minutes of built-in
hold time leading to the opening of the launch window at 9:41 a.m.
(EDT) on July 13. The launch window extends for 2 1/2 hours.

	STS-70 is the fourth mission scheduled for 1995. This will be
the 21st flight of the Shuttle Discovery and the 70th flight overall
in NASA’s Space Shuttle program.

	The primary purpose of mission STS-70 is to deploy the
Tracking and Data Relay Satellite (TDRS-G), the last in a series of a
space-based satellite network that provides communications, tracking,
telemetry, data acquisition and command services essential to Shuttle
and low-Earth orbital spacecraft missions.

	Also, STS-70 marks the first flight of the new Block 1 Space
Shuttle Main Engine, located in the No. 1 position on Discovery.

	Discovery was rolled out of Orbiter Processing Facility bay 2
on May 3 and mated with the external tank and solid rocket boosters
in the Vehicle Assembly Building. The Shuttle stack was then
transported to Pad 39-B on May 11. Discovery had to be returned to
the VAB on June 8 to allow access to the external tank for repairs of
nearly 200 holes in the foam insulation caused by nesting
woodpeckers. The holes were patched and Discovery was returned to Pad
39-B on  June 15. Discovery last flew in February of this year.

	The STS-70 crew are: Commander Tom Henricks, Pilot Kevin
Kregel, and Mission Specialists Nancy Currie, Donald Thomas and Mary
Ellen Weber.

	The crew is scheduled to arrive at KSC at about 4:20 p.m.
Monday, July 10. Their activities at KSC prior to launch will include
equipment fit checks, medical examinations and opportunities to fly
in the Shuttle Training Aircraft.


COUNTDOWN MILESTONES

Launch - 3 Days (Monday, July 10)

* Prepare for the start of the STS-70 launch countdown
* Perform the call-to-stations. All Firing Room console operators
    report on station.
* All members of the launch team report to their respective consoles
    in Firing Room 3 in the Launch Control Center for the start of the
    countdown.
* Countdown begins at 10 a.m. EDT at the T-43 hour mark
* Start preparations for servicing fuel cell storage tanks
* Begin final vehicle and facility close-outs for launch
* Begin stowage of flight crew equipment
* Load backup flight system software into Discovery's general purpose
    computers
* Close payload bay doors for flight (10 p.m.)
* Check out back-up flight systems


Launch - 2 Days (Tuesday, July 11)

Enter first planned built-in hold at T-27 hours for duration of four
hours (2 a.m.)

* Inspect the orbiter's mid-deck and flight-deck and remove crew
    module platforms
* Review flight software stored in mass memory units and display systems
* Clear launch pad of all personnel
* Perform test of the vehicle's pyrotechnic initiator controllers

Resume countdown (6 a.m.)

* Begin the 8 hour operation to load cryogenic reactants into
    Discovery's fuel cell storage tanks

Enter eight-hour built-in hold at T-19 hours (2 p.m.)

* After cryogenic loading operations, re-open the pad
* Resume orbiter and ground support equipment close-outs

Resume countdown (10 p.m.)

* Demate orbiter mid-body umbilical unit and retract into fixed
    service structure
* Start final preparations of the Shuttle's three main engines for
    main propellant tanking and flight


Launch - 1 Day (Wednesday, July 12)

* Activate flight controls and navigation systems
* Install mission specialists' seats in crew cabin
* Close-out the tail service masts on the mobile launcher platform

Enter planned hold at T-11 hours for 13 hours, 21 minutes (6 a.m.)

* Perform orbiter ascent switch list in crew cabin
* Install film in numerous cameras on the launch pad
* Activate the orbiter's communications systems
* Activate orbiter's inertial measurement units
* Fill pad sound suppression system water tank
* Safety personnel conduct debris walkdown
* Move Rotating Service Structure (RSS) to the park position at about
    5:30 p.m.
* Following the RSS move, begin final stowage of mid-deck experiments
    and flight crew equipment

Resume countdown (7:21 p.m.)

* Install time critical flight crew equipment
* Perform pre-ingress switch list
* Start fuel cell flow-through purge
* Activate the orbiter's fuel cells
* Configure communications at Mission Control in Houston for launch
* Clear the blast danger area of all non-essential personnel
* Switch Discovery's purge air to gaseous nitrogen


Launch Day (Thursday, July 13)

Enter planned one-hour built-in hold at the T-6 hour mark (12:21 a.m.)

* Launch team verifies no violations of launch commit criteria prior
    to cryogenic loading of the external tank
* Clear pad of all personnel

Resume countdown (1:21 a.m.)

* Begin loading the external tank with cryogenic propellants (1:21 a.m.)
* Perform inertial measurement unit preflight calibration
* Align Merritt Island Launch Area (MILA) tracking antennas
* Complete filling the external tank with its flight load of liquid
    hydrogen and liquid oxygen propellants (4:21 a.m.)

Enter two-hour hold at T-3 hours (4:21 p.m.)

* Perform open loop test with Eastern Range
* Conduct gimbal profile checks of orbital maneuvering system engines
* Close-out crew and Final Inspection Team proceeds to Launch Pad 39-B

Resume countdown at T-3 hours (6:21 a.m.)

* Crew departs Operations and Checkout Building for the pad 39-B (6:26 a.m.)
* Complete close-out preparations in the white room
* Check cockpit switch configurations
* Flight crew enters orbiter
* Astronauts perform air-to-ground voice checks with Launch Control and
    Mission Control
* Close Discovery's crew hatch
* Begin Eastern Range final network open loop command checks
* Perform hatch seal and cabin leak checks
* Complete white room close-out
* Close-out crew moves to fallback area
* Primary ascent guidance data is transferred to the backup flight system

Enter planned 10-minute hold at T-20 minutes (9:01 a.m.)

* NASA Test Director conducts final launch team briefings

Resume countdown (9:11 a.m.)

* Transition the orbiter's onboard computers to launch configuration
* Start fuel cell thermal conditioning
* Close orbiter cabin vent valves
* Transition backup flight system to launch configuration

Enter final 10-minute hold at T-9 minutes (9:22 a.m.)

* Launch Director, Mission Management Team and NASA Test Director
    conduct final polls for go/no go to launch



Resume countdown at T-9 minutes (9:32 a.m.)

* Start automatic ground launch sequencer (T-9:00 minutes)
* Retract orbiter crew access arm (T-7:30)
* Start mission recorders (T-5:30)
* Start Auxiliary Power Units (T-5:00)
* Arm SRB and ET range safety safe and arm devices (T-5:00)
* Start liquid oxygen drainback (T-4:55)
* Start orbiter aerosurface profile test (T-3:55)
* Start MPS gimbal profile test (T-3:30)
* Pressurize liquid oxygen tank (T-2:55)
* Begin retraction of the gaseous oxygen vent arm (T-2:55)
* Fuel cells to internal reactants (T-2:35)
* Pressurize liquid hydrogen tank (T-1:57)
* Deactivate SRB joint heaters (T-1:00)
* Orbiter transfers from ground to internal power (T-0:50 seconds)
* Ground Launch Sequencer go for auto sequence start (T-0:31 seconds)
* Ignition of three Space Shuttle main engines (T-6.6 seconds)
* SRB ignition and liftoff (T-0)



SUMMARY OF BUILT-IN HOLDS FOR STS-70

T-TIME         LENGTH OF HOLD            HOLD BEGINS           HOLD ENDS
T-27 hours      4 hours	 	      2:00 a.m. Tuesday    6:00 a.m. Tuesday
T-19 hours	8 hours		      2:00 p.m. Tuesday	  10:00 p.m. Tuesday
T-11 hours     13 hours, 21 minutes   6:00 a.m. Wednesday  7:21 p.m. Wednesday
T-6  hours	1 hour		     12:21 a.m. Thursday   1:21 a.m. Thursday
T-3  hours	2 hours		      4:21 a.m. Thursday   6:21 a.m. Thursday
T-20 minutes   10 minutes	      9:01 a.m. Thursday   9:11 a.m. Thursday
T-9  minutes   10 minutes	      9:22 a.m. Thursday   9:32 a.m. Thursday


CREW FOR MISSION STS-70

Tom Henricks	  Commander (CDR)
Kevin Kregel	  Pilot (PLT)
Donald Thomas	  Mission Specialist (MS1)
Nancy Currie	  Mission Specialist (MS2)
Mary Ellen Weber  Mission Specialist (MS3)


SUMMARY OF STS-70 LAUNCH DAY CREW ACTIVITIES

Thursday, July 13

  4:46 a.m.	Wake up
* 5:16 a.m.	Breakfast and crew photo
  5:46 a.m.	Weather briefing (CDR, PLT, MS2)
  5:46 a.m.	Don flight equipment (MS1, MS3)
  5:56 a.m.	Don flight equipment (CDR, PLT, MS2)
* 6:10 a.m.	Crew suiting photo
* 6:26 a.m.	Depart for launch pad 39B
* 6:56 a.m.	Arrive at white room and begin ingress
* 8:11 a.m.	Close crew hatch
* 9:41 a.m.	Launch

* Televised events -- times may vary