Although Glenn's mission had been highly successful, the Mercury operations team was still in the learning process. Experience with a component in the Mercury capsule or a flight procedure during the MA-6 orbital flight served to guide MA-7 mission planning. Glenn had shown that man definitely could be more than just a passenger, so the MSC planners adjusted the MA-7 flight plan to allow more pilot control of the mission. Combined yaw-roll maneuvers were scheduled to permit observation of the sunrise, as well as maneuvers to determine the use of day and night horizons, landmarks, and stars as navigation references. One of the more interesting planned innovations for Carpenter's voyage involved a period of inverted flight (head toward Earth) to determine the effect of Earth-up and sky-down on pilot orientation. Flight planners recognized the need for perceptual reorientation in space flight as well as for the motor skills that had been demonstrated so well by Glenn. The next Mercury mission ought to be as much of a scientific experiment as possible, not only to corroborate MA-6 but also to explore new possibilities with the manned Mercury spacecraft.66
Since Glenn had been able to respond to many of the scientific astronomical observation requests, Homer Newell, who had been Director of NASA's Office of Space Sciences since November 1, 1961, decided that the direction of the scientific portion of the manned space flight program should now become the responsibility of a formal committee. Jocelyn Gill again was chosen to serve as chairman of a group called the Ad Hoc Committee on Scientific Tasks and Training for Man-in-Space. Two days after receiving the mandate, Dr. Gill called a meeting of members, consisting of representatives from the various scientific disciplines, on March 16, 1962, to outline objectives, review past activities in this respect, present a preliminary analysis of the scientific debriefing of Glenn, and outline tasks and goals for the next meeting. One of the aims of the new committee was to devise a curriculum that would provide the astronauts with the best informational sources available about the spatial phenomena they might see. In addition to this, they proceeded to suggest several experiments to the Manned Spacecraft Center.67
So without jeopardizing either pilot safety or mission success, the MA-7 flight would be designed to yield as much scientific, as opposed to engineering, information as possible. Kleinknecht, head of the MSC Mercury Project Office,  named Lewis R. Fisher chairman of the Mercury Scientific Experiments Panel, as a parallel to the NASA Headquarters unit, to manage and arrange for the experiments being suggested. Fisher and his associates were charged with reviewing all proposed experiments from an engineering feasibility standpoint in terms of their scientific value, relative priority, and suitability for orbital flight.68
The Fisher panel first met at Cape Canaveral on April 24, 1962, and decided to emphasize five suggested experiments: releasing a multi-colored balloon that would remain tethered to the capsule, observing the behavior of liquid in a weightless state inside a closed glass bottle, using a special light meter to determine the visibility of a ground flare, making weather photographs with hand-held cameras, and studying the airglow layer - for which Carpenter would receive special training. The tethered balloon was a 30-inch mylar inflatable sphere, which was folded, packaged, and housed with its gas expansion bottle in the antenna canister. The whole balloon package weighed two pounds. Divided into five sections of different colors - uncolored aluminum, yellow, orange, white, and a phosphorescent coating that appeared white by day and blue by night - the balloon was to be cast off near perigee after the first orbital pass to float freely at the end of a 100-foot nylon line. The purposes of the balloon experiment were to study the effects of space on the reflection properties of colored surfaces through visual observation and photographic studies and to obtain aerodynamic drag measurements by use of a strain gauge.69
Some experimentation on the effects of reduced gravity on liquids previously had been conducted at Holloman Air Force Base, at the Air Force School of Aviation Medicine in San Antonio, and at the Lewis Research Center. But the duration of these experiments, involving parabolic airplane flights and drop-tower tests, had been necessarily short. Results of an extended study would have both immediate and long-range implications in manned space flight operations. Already the problem of gas or fuel vapor ullage in space vehicles and in storage tanks was causing some difficulties, and later there would be related problems in orbital rendezvous fuel transfer. Before fuel tanks and pumps for extended use in space could be designed, the behavior of surface tension and capillary action of liquids in the weightless state had to be determined. For this experiment the Lewis Center provided a small glass sphere containing a capillary tube with tiny semicircular holes at the bottom of the open tube. The sphere, only 20 percent filled, contained 60 milliliters of a mixture of distilled water, green dye, aerosol solution, and silicone. The liquid had a surface tension of 32 dynes per centimeter on Earth.
The Massachusetts Institute of Technology requested photographs of the daylight horizon through blue and red filters to define more precisely the Earth-horizon limb as seen from above the atmosphere. These findings would be particularly valuable for navigation studies in the Apollo program. The Weather Bureau wanted information on the best wavelengths for meteorological satellite photography. John A. O'Keefe and Jocelyn Gill at the Goddard Space Flight Center  and NASA Headquarters, respectively, wanted a distance measurement of the airglow layer above the horizon, its angular width, and a description of its characteristics, and for this experiment Carpenter was provided with a photometer and trained to use it. Paul D. Lowman, also of Goddard, requested special photography of the North American and African land masses. Lowman's interest was based on his studies of planetary surfaces, particularly regarding meteoroid impact features.70
A number of technical changes based on MA-6 mission results were made for MA-7, mostly involving deletions of certain equipment from the spacecraft to reduce weight. Kleinknecht's office eliminated the sofar bombs and radar chaff recovery aids, which seemed unnecessary in view of the effectiveness that had been demonstrated by the sarah beacon and dye markers. Other deletions included the knee and chest straps on the couch, which had bothered Grissom; the red filter in the window; the moderately heavy Earth-path indicator; and the instrument panel camera, which had already gathered sufficient data.
Modifications made to improve spacecraft, network, and astronaut performance included a radio frequency change in the telemetry system to eradicate transmission interference like that experienced on Glenn's flight. The two landing-bag switches were rewired so that both had to be closed to activate the deploy signal. To correct temporarily the control problem experienced by Glenn, Karl F. Greil of the Mercury Project Office studied masses of data and concluded that the problem lay in the fuel line filters. So the dutch-weave filters in the fuel lines were replaced with platinum screens, and a stainless-steel fuel line was substituted. This was intended as an "interim fix," but it became permanent in the Mercury project for the later flights. Even the astronaut's attire underwent some modifications. Pockets were added on the upper sleeves and on the lower legs of the pressure suit for pencils, a handkerchief, and other small accessories. And the waterwing life vest, first carried by Glenn, was installed on the chest beneath the parabolic mirror. To add to Carpenter's comfort while he was waiting in his capsule on the launch pad, a new and more resilient liner was fitted in the couch.71
The three principal components of the MA-7 mission - spacecraft, launch rocket, and astronaut - were in preparation for several months. Spacecraft No. 18 was the first of these to reach the Cape, arriving on November 15, 1961. During its long checkout period by G. Merritt Preston's crew, this vehicle was reworked twice to incorporate lessons learned during MA-5 and MA-6. Some equipment and systems in the capsule had to be exchanged because what it had carried to Florida simply did not work properly. The original periscope, for example, failed to latch in the retracted position. Glenn's drogue parachute mortar supposedly had fired before the pilot triggered its button; the McDonnell engineers decided that a barostat in the recovery arming circuit should prevent another premature action. Since there still were questions concerning the temperature at different places on the capsule while it was in orbit, a device known as a  "low-level commutator" was added, and temperature pickups were strategically located at 28 points on the spacecraft to record temperature data on a tape recorder carried on board.72
When in March he learned that he would fly spacecraft No. 18, Scott Carpenter named his capsule Aurora 7. He chose this name deliberately, "Because I think of Project Mercury and the open manner in which we are conducting it for the benefit of all as a light in the sky. Aurora also means dawn - in this case the dawn of a new age. The 7, of course, stands for the original seven astronauts." Coincidentally, the astronaut as a boy had lived at the corner of Aurora and Seventh Avenues in Boulder, Colorado.
The Atlas, the astronaut, and the ground support personnel entered into their final preparatory phase in March 1962. On March 8, six days after the Air Force accepted it at the rollout inspection at the Convair factory in San Diego, Atlas 107-D arrived at the Cape and was erected on the pad. Since the previous Atlas had performed well in boosting Glenn into orbit and since the MA-7 launch requirements were to duplicate those of MA-6, few changes were necessary for 107-D. One alteration was a slight reduction in the staging time, from 131.3 to 130.1 seconds after liftoff, to improve the launch vehicle's ability to reach the precise center of the insertion "window."73 Intensive training for the astronaut, his backup, and the tracking teams on the MA-7 mission began on March 16. Mission simulations, flight controller training, and an exercise of the Defense Department recovery forces proceeded much as they had for MA-6. The Atlantic tracking ship, however, was not on station for MA-7 because she was at a Baltimore shipyard, being converted into a command ship to support the longer duration Mercury missions.74
At the time of Glenn's flight, the launch of MA-7 had been scheduled for the second week in April, but the installation of new components, such as the temperature survey instrumentation and the barostat in the drogue parachute circuit, as well as other work, delayed the launching until May. Also contributing to the postponement was an Atlantic Fleet tactical exercise that required participation by the recovery ships and aircraft for several weeks. The week beginning May 20 looked the most feasible for sending a second American into orbit.75
65 Slayton, interview, Houston, Jan. 14, 1965; "Postlaunch Memorandum Report for Mercury-Atlas No. 7 (MA-7), Part I, Mission Analysis," NASA/MSC, June 15, 1962. After MA-7 each backup pilot became the flight astronaut of the succeeding mission in Project Mercury. Also see Loudon Wainwright, "Comes a Quiet Man to Ride Aurora," Life, LII (May 18, 1962).
66 "Technical Information Summary for Mercury-Atlas Mission 7 (MA-7, Spacecraft 18)," MSC, undated.
67 Gill interview; NASA, "Summary Minutes: Ad Hoc Committee on Scientific Tasks and Training for Man-in-Space (Meeting Nos. 1, 2, 3)," March 16, 26, and April 18, 1962.
68 NASA News Release 62-113, "MA-7 Press Kit," May 13, 1962.
69 "Project Mercury Mission Directive for Mercury-Atlas Mission 7 (MA-7, Spacecraft 18)," NASA Project Mercury working paper No. 222, April 9, 1962; "Postlaunch Memorandum Report for MA-7"; Results of the Second United States Manned Orbital Space Flight, May 24, 1962, NASA SP-6 (Washington, 1962), 11-13. In the order listed in the text, the experiments were proposed by the Langley Research Center, Lewis Research Center, Massachusetts Institute of Technology Instrumentation Laboratory, the Weather Bureau, and Goddard Space Flight Center.
70 Ibid. Airglow is an emission of light resulting from chemical reactions in the upper atmosphere. Various reactions produce light of different colors. In many cases, molecules of atmospheric gas are split by ultraviolet rays of sunshine. Then, when darkness comes, the gas molecules recombine, emitting light. The illumination of the sky at night usually comes from airglow instead of starlight. New York Times, June 3, 1962. Lawrence Dunkelman of Goddard provided Carpenter with the airglow device to make observations. Jocelyn Gill said this was the filter that had been planned for MA-6, but time did not permit Glenn to use it.
71 Ibid.; "Project Mercury Quarterly Status Report No. 14 for Period Ending April 30, 1962," NASA/MSC, May 25, 1962. John Mayer of MSC commented in September 1965, "that photos of the Russian spacecraft indicated that they had an almost identical earthpath indicator." Mayer went on to say that the indicator "was deleted from Mercury flights because it was of little use in the missions."
72 "Project Mercury Mission Directive for Mercury-Atlas Mission 7"; message, G. Merritt Preston to Gilruth, May 21, 1962; "Weekly Activity Report to the Office of the Director for Manned Space Flight," MSC, May 5, 1962.
73 "Project Mercury Quarterly Status Report No. 14"; "Weekly Activity Report," MSC/Mercury Project Office, March 17, 1962; "Postlaunch Memorandum Report for MA-7."
74 Memo, Kraft to Williams et al., "MA-7 Test Flight Reports," June 12, 1962; "Project Mercury Mission Directive for Mercury-Atlas Mission 7"; Final Report to the Secretary of Defense on Support of Project Mercury, Chart 6, 15. The Indian Ocean picket ship Coastal Sentry (call name "Coastal Sentry Quebec") was stationed at the entrance to the Mozambique Channel off the southeastern coast of Africa for MA-7. "MA-7 Press Kit."
75 "Project Mercury Quarterly Status Report No. 14." The decision to add a barostat in the recovery arming circuit was a primary reason for delaying the MA-7 launch. After a review meeting on May 16, the engineers had decided that this action was necessary. Late that night the newsmen already at the Cape were advised.