Also, Gemar set up a model of the scaffold-like truss structure that may be used on a future space station in the lower deck. The model, linked to sensitive recorders in a shuttle locker, was used to determine the characteristics of such structures in orbit. The model and its reactions were studied in several different configurations during the day.
Other activities for the crew included photography of the glow created as the shuttle's outer skin interacts with atomic oxygen in orbit and continued monitoring of protein crystal growth experiments in the cabin.
Although not highly visible except to the Earth-bound scientists watching over them, Columbia's wide assortment of cargo bay payloads continued their investigations throughout the day. The second United States Microgravity Payload (USMP-2) experiments, continue to produce a wealth of data for scientists on the ground.
The Critical Fluid Light Scattering Experiment, or ZENO, science team reported that they expect to locate the critical temperature of xenon at "any time." Team members closely watched computer data traces which indicate their experiment was very near the critical temperature -- the goal of a lengthy, methodical "sensitive" search process. This is a more precise search for the critical temperature after its location has been determined within a narrow band. Once the temperature is located, the team will spend nearly 24 hours taking a good look at the phenomenon they've waited years to see. They will study the properties of xenon at its critical point, taking subtle optical measurements in the region surrounding it. A fluid's "critical point" occurs at a condition of temperature and pressure where the fluid is simultaneously a gas and a liquid. By understanding how matter behaves at the critical point, scientists hope to gain a better insight into a variety of physics problems ranging from phase changes in fluids to changes in the composition and magnetic properties of solids.
The Space Acceleration Measurement System (SAMS) continued to measure the microgravity environment on the USMP-2 carrier in support of the four other experiments onboard. The SAMS team began sending results of their data collection during various orbiter activities to STS-62 crew members. The crew was interested in how they can minimize their influence on the microgravity environment. Measurements are made with the system at specific times when microgravity disturbances may be caused by events such as crew exercise and movement of the Shuttle's Ku-band antenna. Such observations also collect "signatures" which the team will be able to easily identify in future data.
A related system, the Orbital Acceleration Research Experiment (OARE), is managed by NASA's Johnson Space Center. It is useful on missions such as USMP-2 where it is important to accurately characterize a wide variety of disturbances in the microgravity environment. Working closely with SAMS, the OARE records any low-frequency activity such as the Shuttle's friction with the rarefied upper atmosphere. SAMS is most suitable for recording higher-frequency activity such as crew exercise. The OARE instrument continues to process data in support of the USMP-2 experiments, and team members say all is going well.
The Isothermal Dendritic Growth Experiment (IDGE) continued to assemble data to test theories concerning the effect of gravity-driven fluid flows on dendritic solidification of molten materials. When the USMP-2 mission is over, the IDGE team will study hundreds of photographs taken of the dendrites grown in microgravity. Learning more about how dendrites grow is one valuable key to developing better metal products and improving our industrial competitiveness.
Upon completion of its first phase of pre-programmed operations last night, the dendritic experiment entered its second phase of crystal growth when team members began sending commands to their experiment from the ground using a unique set of capabilities known as "telescience." This allows them to get the best possible data from their investigation.
The Advanced Automated Directional Solidification Furnace (AADSF) studies the directional solidification of semiconductor materials in microgravity. Downlinked experiment data indicates that solidification of a crystal of mercury cadmium telluride is taking place, and the AADSF science team is constantly monitoring this slow but steady progress. Testing the AADSF in microgravity is beneficial because on Earth, gravity causes fluids to rise or fall within the melted portion; a warm liquid is less dense than a cool one and will rise to the top of the melt. These convective movements of molten material contribute to physical flaws in the internal structure of the growing crystal. Such flaws affect a crystal's overall electrical characteristics, and consequently, its usefulness in electronic devices.
The MEPHISTO team reported that they have gathered good data with their directional solidification furnace. Currently, however, the team is still troubleshooting a problem discovered on Saturday night with a troublesome "Seebeck measurement." This electronic signal measures changes in the microstructure of a solidifying metal, and is conducted on one of three experiment samples of bismuth-tin. Other measurement techniques will be used on the two remaining samples later in the mission; both these samples are operating nominally. Measurement data from the three samples will give scientists insight into the precise nature of solidification in reduced gravity.
Flight controllers had a quiet Sunday in Mission Control with no significant troubles seen aboard the spacecraft. A reading of high pressure that was seen in a fuel line to one of the shuttle's three auxiliary power units earlier in the flight has dissipated, and controllers have confidence the APU would operate well if needed. However, they will continue to closely watch the readings from that area. All of the three APUs, which supply power to the hydraulic systems, operated well during launch. They are not used again until landing. The crew began eight hours of sleep at 4:53 p.m..
After completing their post-sleep activities, the crew got started on the payload work for the day. Astronauts performed checks of the protein crystal growth experiment and the rodents that are housed in the middeck as part of the Physiological Systems Experiment. Gemar also continued his work with the Middeck 0-Gravity Dynamics Experiment. MODE is designed to study the fundamental, non-linear, gravity-dependent behavior of hybrid scaled structures. Understanding these structures is important for designers of large space structures such as the International Space Station.
Casper conducted a special presentation about the Space Acceleration Measurement System. A frequent flyer on the shuttle, SAMS uses sensors called accelerometers to take measurements of on-board vibrations and accelerations. Such disturbances, though slight, could affect the sensitive microgravity experiments. SAMS measurements allow scientists to adjust their experiments to improve their scientific results.
Columbia astronauts Andrew M. Allen and Charles D. Gemar got a half day off from their busy schedule operating the many microgravity experiments on STS-62. Due to the long duration of STS-62, each crew member will get two half-days off during the 14 day mission.
The other astronauts spent the first half of the day working with the Middeck 0-Gravity Dynamics Experiment, or MODE, and a model of a truss structure which may be used on a future space station. The truss model, set up to float free in the middeck, was analyzed to determine its behavior in weightlessness. It will be the subject of more test runs as the flight progresses.
Around the clock, experiments with the U.S. Microgravity Payload-2, the Office of Aeronautics and Space Technology-2, the Space Shuttle Backscatter Ultraviolet instrument and the Limited Candidate Duration Materials Exposure experiments all continue to operate, many of them being controlled by scientists on the ground. The SSBUV instrument operated since the first day of the flight, and plans were made by its ground controllers today to attempt to detect sulfur dioxide emissions from volcanoes in Central America. The objective of the observations by SSBUV are to investigate whether such emissions low in the atmosphere are detectable from orbit. SSBUV's measurements in general are used to fine-tune satellites that monitor the ozone and other gases in the Earth's atmosphere. The crew began its eight hours sleep period at 4:53 p.m. EST.
During USMP-2 operations on Flight Day 4, the Critical Fluid Light Scattering Experiment, or ZENO, team reported overnight that they started seeing behavior in the fluid xenon unlike any they have seen on Earth. They believe this may mean the experiment has passed through the xenon sample's critical point. Meanwhile the team continued their delicate temperature manipulations in order to verify what they have seen. Once the team is certain they have located the critical point, they will conduct a series of precise measurements in the area surrounding it using laser light scattering. When xenon is at or extremely near its critical point -- the point where it is simultaneously a liquid and a gas -- patches of the otherwise clear substance briefly take on a "milky" iridescence. Closer to the critical point, the milky-white areas are larger and exist for longer periods. When a laser light is passed through the sample in these areas, fluctuations in the sample's density cause the light to be scattered.
Team members for the MEPHISTO furnace began running a series of metal solidification studies and received analyzable data. On Monday, the team made much progress in overcoming some difficulty they had been experiencing with one of the experiment's electronic measurements and successfully completed a Seebeck run. The Seebeck measurement is an electrical signal which measures temperature variations during crystal growth at the boundary where liquid becomes solid -- the solidification front. MEPHISTO is used to conduct a series of melting and solidification cycles on three identical rod-shaped samples of a bismuth-tin alloy. During these runs, temperature, velocity and shape of the solidification front are measured in order to study the behavior of metals and semiconductors as they solidify.
Team members of the Isothermal Dendritic Growth Experiment (IDGE), say they were pleased with the performance of their apparatus and the data they acquired during USMP-2. While dendrite growth was taking place, two 35mm cameras took photographs for post-mission analysis. When a dendrite growth cycle is completed, the tiny crystalline structure is re-melted and another grown at a different "supercooling" temperature. Dendrites were grown at 20 different levels of supercooling ranging up to approximately 1.3 degrees Celsius. Supercooling is the term used to describe the condition in which a liquid is slowly cooled to below its normal freezing point, but due to its purity, does not solidify. The level of supercooling refers to the difference between the temperature of the liquid and its normal freezing point. IDGE is a fundamental materials science experiment performed in the microgravity environment of space in order to increase understanding of the solidification processes. This knowledge should be useful in improving industrial production of a wide range of metals used in applications from aluminum foil to jet engines.
The Advanced Automated Directional Solidification Furnace (AADSF) continued to operate smoothly, growing a single cylinder-shaped crystal of mercury cadmium telluride, an exotic material used as an infrared radiation detector. The AADSF provides scientists with a unique apparatus in which to test theories of semiconductor crystal growth without the effects and limitations caused by Earth's gravity. The information gained by growing crystals of a semiconductor material in microgravity can be used to study the physical and chemical processes of many materials and systems. A greater understanding in these areas could aid researchers in the discovery of processes and materials that perform better and cost less to produce.
The crew was awaken at 11:53 p.m. for the start of Flight Day Five activities. The middeck payloads took center stage as the STS-62 crew worked through the second half of its fifth day on orbit. Pilot Andrew M. Allen (1 h 45 min) and Mission Specialist Sam Gemar (1 h 45 min) took turns in the Lower Body Negative Pressure Unit. The sack-like device seals at the waist so that pressure around the lower body can be gradually decreased. The lowered pressure draws body fluids down to the legs and lower torso, similar to the body's normal state on Earth. The LBNP protocol is being tested as a countermeasure to the condition "orthostatic intolerance" in which a person feels lightheaded after standing. Some astronauts experience such sensations upon standing after the shuttle lands. Today, Allen and Gemar performed the 45-minute ramp test, but at the direction of ground controllers, terminated the test 40 seconds early.
STS-62 Commander John Casper, Mission Specialist Pierre Thuot and Mission Specialist Marsha Ivins relaxed on board Columbia for the first half of the day. On long duration flights, mission planners schedule off duty time for each crew member to keep them well rested throughout the flight. Gemar and Allen had their off duty time on Monday.
With those activities complete, the crew turned its attention to the assortment of secondary payloads. Astronauts checked on the protein crystal growth experiments, the Commercial Generic Bioprocessing Apparatus experiments and the rodents which were flying as part of the Physiological Systems Experiment. They also continued the Middeck 0- Gravity Dynamics Experiment activities.
On Flight Day 5 (Tuesday, March 8, 1994) Columbia's crew continued a daily regimen of daily exercise, photography and monitoring the progress of crystal growth and bioprocessing experiments aboard the Shuttle.
Meanwhile, ground-based researchers remotely operating experiments in Columbia's cargo bay continued their observations. Scientists working with the Space Shuttle Backscatter Ultraviolet instrument continued probing the layers of Earth's atmosphere and recorded data on tropospheric emissions from Mexican and Central American volcanoes; sulfur dioxide from industrial by-products in the troposphere above China and Japan; and observations in the mesophere above the Mexican volcano Colima.
Among the experiments of the Office of Aeronautics and Space Technology-2 package, materials being designed for future spacecraft in the SAMPIE experiment were exposed to the orbital environment for the first time. Results included the operation of an advanced solar energy cell and plasma interactions with various materials while the Shuttle's payload bay was pointed toward Earth.
Other OAST-2 accomplishments included 10 freeze and thaw cycles of a new cooling technology for future spacecraft; spectrometer readings of airglow phenomena in the upper atmosphere with the EISG instrument; and studies of the Shuttle's interaction with atomic oxygen using the SKIRT instrument.
Three members of the crew had a half-day off (Casper, Thuot, Ivins), and all of the crew will get one more half-day off before the mission, planned as the second longest in history, concludes on March 18. Columbia is operating well with few problems encountered by the crew or Mission Control. The spacecraft remains in an orbit with a high point of 163 nautical miles (302 km) and a low point of 161 nautical miles (298 km). The crew began eight hours of sleep at 2:53 p.m. central and will awaken at 10:53 p.m. central to start a sixth day in space.
Pilot Andy Allen took time from his day to talk with reporters in Cleveland, Ohio; Philadelphia, Penn.; and Knoxville, Tenn. Prior to his interview, Allen discussed the medical tests that crew members are performing before during and after the flight. Astronauts are collecting blood and urine samples to help researchers determine the chemical regulatory changes the human body undergoes while in space. Pre- and post-flight test study the crew members' gait, steadiness while standing and exercise capacities.
Other crew members checked on the protein crystal growth experiments, performed some Auroral Photography experiments and checked the orbiter windows for any debris impacts. Later today, crew members will exercise using the Shuttle's ergometer.
Spacelab Mission Operations Control at the Marshall Space Flight Center reported the second United States Microgravity Payload (USMP-2) completed yet another day of successful operations in orbit aboard the Space Shuttle Columbia.
On Tuesday, scientists with the Critical Fluid Light Scattering Experiment, or ZENO, concluded that they had indeed pinpointed the location of the long-sought-after critical point of the substance xenon. For the next 24 hours, a series of subtle optical measurements will be made in the area surrounding this phenomenon where a fluid acts like both a liquid and a gas.
Critical point experiments are difficult to perform on Earth because at the critical point the fluid becomes highly compressible, or elastic. The sample being studied cannot be maintained at the critical point because the substance's own weight compresses part of the sample to a density greater than that of the critical density. This causes the sample to literally collapse under its own weight. During USMP-2, researchers have found that the absence of gravity has the effect of "widening" the critical zone, giving them a much "crisper" picture of the critical point phenomenon and allowing them to take measurements not possible on Earth.
In the materials science field, the Advanced Automated Directional Solidification Furnace (AADSF) continued to grow a single crystal of mercury cadmium telluride in the microgravity environment of the Shuttle cargo bay. The AADSF scientists say that telemetry from their experiment indicates crystal growth is proceeding "exceptionally well." By using a furnace with three temperature zones -- each independently controlled -- and growing the crystal slowly in one direction, a flatter solidification front, or crystallization boundary, is achieved. This grows a crystal that will allow a more detailed post-mission study of the influence of gravity on crystal defects and chemical component distribution.
After several days of successfully growing crystalline dendrites in microgravity, team members for the Isothermal Dendritic Growth Experiment (IDGE) report that their instrument can do what it was designed to do and more. The team reports they are very pleased with the performance of the IDGE as well as the number and quality of the dendrites grown so far during the STS-62 mission. The IDGE experimenters will continue to monitor slow-scan video images of dendrites growing in their apparatus in order to maximize the efficiency of the instrument and the science results.
The Space Acceleration Measurement System (SAMS) continued to provide a running account of vibrations aboard the Shuttle to the other USMP-2 experiment teams. It recorded detailed measurements to characterize how smooth and stable a platform Columbia is providing for the experiments. SAMS has flown eight times previously, and is scheduled for all upcoming USMP flights, in a continuing program to enhance understanding of the microgravity environment.
Columbia also changed attitudes for the first time since launch day. Columbia orbited with its tail pointing toward the Earth and the payload bay pointing in the direction of travel or the "ram" position. With the maneuver, Casper closed and opened sample trays for the Long Duration Space Environment Candidate Material Exposure (LDCE) experiment. The LDCE consists of three identical sample plates with 264 samples of various materials used in space vehicles. One of the sample plates will be exposed to the space environment for most of the mission. One will be exposed only when the payload bay is pointing in the ram position - or pointing into the direction of travel - and a third is exposed only when the orbiter is not in the ram position.
Mission Specialist Marsha Ivins was interviewed by students at the Bronx High School of Science. The students asked a variety of questions about the microgravity experiments being conducted during the mission on living and working in space.
Also, Mission Specialist Sam Gemar and Pilot Andrew M. Allen each completed 45-minute ramp tests in the lower body negative pressure unit, and performed more tests with the Middeck 0-Gravity Dynamics Experiment. Astronauts also performed the standard checks of the protein crystal growth and rodent experiments housed in Columbia's middeck.
Flight controllers in Houston put the finishing touches on a plan to uplink more digital video to the crew on Flight Day 9. The plan required procedural changes on the ground, but no action by the crew. The STS-62 crew began its sleep shift on time at 1:53 p.m. CST, and was scheduled to be awoken at 9:53 p.m. CST to begin its ninth day of orbit operations.
During an in-flight news conference, the crew responded to questions ranging from budget cutbacks and safety, to experimentation and life on the planned international space station. Activities in the Mission Control Center focused on preparing, reviewing and uplinking messages outlining changes to the crew's scheduled activities for flight day eleven in space. The crew began its standard eight hour sleep shift a little before 2 p.m. and is scheduled to wake up at 9:53 p.m. CST.
Awakened for their tenth day in space to the song "Starship Trooper" performed by the group Yes, Columbia's crew started the day by lowering the Shuttle's orbit by about 20 nautical miles (37 km) and shifting the focus of science onboard to the second major goal of the flight.
Experiments and observations in the cargo bay focused on the interaction of the Shuttle with atomic oxygen, nitrogen and other gases in orbit, an interaction that causes a well-known glowing effect around the surfaces of the spacecraft. The lower orbit increases the effect, and instruments with the Office of Aeronautics and Space Technology-2 (OAST-2) package have now taken center stage for the mission.
Early in the morning, Commander John Casper and Pilot Andy Allen fired Columbia's orbital maneuvering system engines twice to descend from a 161 by 157 nautical mile (298 by 291 km) high orbit to a 140 nautical mile (259 km) circular orbit. Shortly thereafter, observations by OAST-2 began with a three-minute release of nitrogen gas from a canister in the cargo bay and a study of its effect on the glow of a special plate, constructed of materials that may be used on future satellites. Later, Columbia, with tail pointed toward Earth, performed a 25 minute long series of 360 degree spins to allow observations by OAST-2's Spacecraft Kinetic Infrared Test instrument. Such observations by both instruments will set the pace for the ensuing days of the flight.
Mission Specialists Marsha Ivins and Sam Gemar each took a turn evaluating a tracking system for Columbia's mechanical arm today as well. Part of the Dexterous End Effector (DEE) experiment, the system uses a mirror near the end of the arm, flashing light-emitting diodes, a cargo bay camera and a portable computer to assist an astronaut in finely aligning the arm, an alignment that may one day be required for delicate construction tasks. Each crew member also took a turn at exercise as has been the daily routine during the long-duration flight.
The astronauts continued to work with these experiments for the remaining part of their day, and began an eight-hour sleep period at 1:53 p.m. central and awaken at 9:53 p.m. to start Day Eleven. On its 159th orbit, Columbia was in excellent condition and flight controllers have noted no new problems with the spacecraft's systems.
As payload cameras showed the Earth vista from 140 nautical miles (259 km) up, the STS-62 crew of Columbia sent a special goodnight message -- the Bette Midler song "From a Distance" -- for the men and women watching over them from below in Houston.
The message came at the end of a busy 11th day of on-orbit operations that featured a shift in focus from United States Microgravity Payload-2 to work with the Office of Aeronautics and Space Technology-2 (OAST-2) package.
Observations in the cargo bay are now concentrating on the interaction of Shuttle surfaces with atomic oxygen, nitrogen and other gases as they ram through the rarefied atmosphere at 17,500 miles an hour (28,200 km/h). Early in the day, Commander John Casper and Pilot Andy Allen lowered Columbia's orbit by 20 nautical miles (37 km) to support the OAST-2 shuttle glow observations.
Mission Specialists Marsha Ivins, Sam Gemar and Pierre Thuot each took a turn evaluating a tracking and grapple system for Columbia's robot arm. The Dexterous End Effector (DEE) demonstration also looked at the forces generated by arm movements when its magnetic end effector was engaged. The forces were recorded by a Force Torque Sensor that also is part of the DEE equipment.
The astronauts were scheduled to awaken at 9:53 p.m. to start their 12th day of work in space. Columbia is in excellent condition and flight controllers have noted no new problems with the spacecraft's systems.
Mission Specialists Marsha Ivins, Pierre Thuot and Sam Gemar took turns operating the arm to test new technology called the Dexterous End Effector (DEE). DEE includes a magnetic grasping mechanism, a sensor that determines the force being applied by the arm and displays that information to the operator, and a tracking system that allows the arm to be precisely aligned.
The crew gave good reviews to the technology during the morning, testing it by using the 50 foot (15 m) long arm to insert pins into sockets that had progressively smaller clearances, ranging from 12/100ths of an inch (3 mm) of clearance for the loosest to 3/100ths of an inch (0.76 mm) for the tightest. Later, a foot (300 mm) wide flat beam was inserted into a slot and then moved back and forth to correlate readings by the force sensor, technology that also was highly complimented by the crew.
While DEE operations progressed on the flight deck, Gemar and Pilot Andy Allen each had one ramp session in the Lower Body Negative Pressure (LBNP) device. A medical experiment, LBNP imitates gravity by using low air pressure around the lower half of the body to pull body fluids downward. Body fluids shift upward in weightlessness, away from the lower extremities, and LBNP, in addition to gathering medical data, serves to counteract this effect and helps astronauts more easily readapt to gravity upon their return to Earth.
The Office of Aeronautics and Space Technology-2 payload took center stage among the scientific investigations in the payload bay. The crew cooperated with investigators of the Experimental Investigation of Spacecraft Glow instruments, positioning the robot arm's camera above its sample plate in between DEE runs. A low-light camera in the payload bay that was supposed to have recorded the effects of gaseous nitrogen releases and their effect on shuttle glow failed earlier in the mission.
The Space Shuttle Backscatter Ultraviolet instruments in the payload bay also continued to take readings that will be used to help calibrate free-flying satellites that continually monitor the ozone content of Earth's atmosphere.
The crew began an eight-hour sleep shift at 1:53 p.m. CST, and will be awakened at 9:53 p.m. CST. About 2:08 a.m. CST, a fifth orbital maneuvering system burn will lower the perigee of Columbia's orbit to 105 nautical miles (194 km) for additional spacecraft glow measurements.
Columbia's Commander John Casper and Pilot Andy Allen started out their 13th day in orbit with an eye toward the trip home, performing a standard check of the systems Columbia will use for entry and landing.
For the first part of the morning's flight control systems checkout, the crew used auxiliary power unit 3, one of three units that supply power for the spacecraft's hydraulic systems during launch and landing. APU 3, which had been the subject of scrutiny early in the mission due to high pressure readings in a fuel line, operated normally.
Following the checkout, the crew fired Columbia's orbital maneuvering system engines for 38 seconds, dropping one side of the Shuttle's orbit by about 35 nautical miles (65 km) to the lowest orbital altitude of any Shuttle flight to date. Columbia is now in an elliptical orbit with a high point of 140 nautical miles (259 km) and a low point of 105 nautical miles (194 km). The lower orbit is required for continuing observations of the glowing effect created as the Shuttle interacts with atomic oxygen and other gases in low orbit.
During the first shuttle glow observations in the new orbit, Mission Specialist Pierre Thuot reported the glowing effect was much more pronounced at the lower altitude. The crew also activated the Limited Duration Candidate Materials Exposure, or LDCE, experiment, exposing materials to the low-orbit environment that are under study for use on future spacecraft. The crew also began another series of evaluations of the Dexterous End Effector equipment using the shuttle's mechanical arm, testing the technology's magnetic grapple system, alignment system and force sensor.
The crew was awakened by the song "Traveling Prayer" performed by Billy Joel. Columbia remains scheduled for a landing Friday morning.
Columbia's five astronauts this morning performed final checks of their spacecraft, wrapped up their experiments and began packing their bags in preparation for the return to Earth.
Columbia was scheduled to fire its orbital engines at 6:18 a.m. Central on Friday to begin a descent that will culminate with a touchdown on the Kennedy Space Center Shuttle Landing Facility runway at 8:09 a.m. EST. Weather conditions in Florida are forecast to be favorable for the landing.
Commander John Casper and Pilot Andy Allen test-fired Columbia's 38 primary steering jets early this morning, finding them all in good shape for the trip home. Later, Casper and Allen each spent time practicing landings using a portable computer simulation designed for the Shuttle.
Meanwhile, Mission Specialist Sam Gemar spent four hours in the Lower Body Negative Pressure Device (LBNP) a medical device that may assist astronauts to more easily readapt to Earth's gravity. The LBNP is a bag-like device that lowers the pressure around the lower half of the body, pulling body fluids down in an imitation of the effects of gravity on the body.
Mission Specialist Marsha Ivins powered down Columbia's mechanical arm and latched it in its cradle for the trip home, and Pierre Thuot completed operation of the two protein crystal growth experiments onboard, preparing them for the entry and landing.
Several final observations of the Shuttle glow effect, a phenomenon created as atomic oxygen and other gases impact the spacecraft, were conducted. Columbia performed another series of spins for the investigations that included more releases of nitrogen gas from cargo bay canisters.
The final few hours of the crew's day will be devoted to stowing gear and preparing Columbia for the mission's end. Columbia is in an orbit with a high point of 139 nautical miles (257 km) and a low point of 105 nautical miles (194 km).
The Flight Day 15 (Friday, March 18, 1994) plan called for deorbit preps and a deorbit burn of 209 ft/s (63.7 m/s) at MET 13/22:04 with a planned landing at KSC. Landing occurred at KSC 3/18/94 at (approx) 8:10 a.m. EST. Runway 33.