The NASA Public Affairs Office issued a press release prior to the flight, stating "The men in charge of Project Mercury have insisted on orbiting the chimpanzee as a necessary preliminary checkout of the entire Mercury program before risking a human astronaut.

Seven Atlas launches since September, including four failures, were reviewed for any items of interest but most were not of concern to Mercury.

Atlas 32E, also carrying a monkey on a biological mission, experienced a sustainer shutdown and was destroyed by Range Safety action shortly after liftoff on November 10 but the failure was due to an improperly installed component that was not of concern to the more tightly supervised Mercury program.

Although MA-4 had performed well, there was still some concern about high vibration levels during the first 20 seconds of liftoff, so the autopilot on MA-5's booster was modified slightly to correct this problem.

Prelaunch preparation proceeded relatively smoothly, with a number of minor repairs, including a potentially serious problem with the vernier engines not being bolted in place tightly, which could have resulted in damage to the airframe during launch.

The Range Safety system on Atlas 93D was modified so that a manual cutoff command could be sent to the sustainer engine.

A more compact all-solid state telemetry unit replaced the bulky vacuum tube-based package used previously.

Gus Grissom's flight on MR-4 had used a Mark II capsule, but it was necessary to test it on a proper orbital mission to ensure that the large window could handle the much higher heat of reentry there.

Enos's backups were (in order of possible call-up) Duane, Jim, Rocky, and Ham (the Mercury-Redstone 2 veteran).

The modified autopilot apparently worked as vibration remained within comfortable levels and the boost phase was uneventful.

The Mercury Control Center at Cape Canaveral received information that all spacecraft systems were in good condition.

As the MA-5 passed over the Atlantic tracking ship at the beginning of the second orbit, indications were received that inverter temperatures were rising.

Abnormal heating had occurred on earlier flights; in such cases, inverters had continued working or had been switched to standby.

When the spacecraft reached Muchea, Australia, high thruster signals and capsule motion excursions were detected.

When the MA-5 crossed the tracking station at Woomera, Australia, attitude control problems were not detected, so earlier reports were discounted.

However, the engineering team were concerned about the stuck thruster causing high fuel consumption, so they advised terminating the flight before the capsule ran out of attitude control gas.

Flight Director Christopher Kraft alerted the Hawaii controllers to be ready to initiate retrofire to bring the spacecraft down in the Pacific, if necessary.

The spacecraft and Enos were both found to have survived the mission in good condition, although the chimpanzee had removed all of the medical electrodes and the urine collection device from his body.

This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.