The SBI Gondola

For the balloon flight of the SBI we use the same gondola and subsystems previously developed and employed for the Flare Genesis Experiment (FGE) project. During the past 8 years this gondola and its subsystems have undergone many improvements and upgrades and it is now a proven observing platform.

The gondola basic design was derived from a payload developed by the Harvard/Smithsonian Center for Astrophysics (CFA). Standard aluminum angles bolted together are the main components of the gondola frame. high. It is strong enough to support up to 2000 kg (4400 lb) even under the 10g pull that could be experienced at the end of a flight when the parachute inflates several seconds after the balloon cut-off. In addition, it is rigid enough to allow the required telescope pointing stability. In addition, it is rigid enough to allow stable telescope pointing. The payload dimensions are: 2 m wide, 1.5 m deep, and about 4.5 m.

The Main Telescope (MT) is mounted to the frame on the elevation (pitch) axis. It can pivot around this axis by means of a torque motor whose stator is connected to the gondola and its rotor to the MT cage. During launch and landing, the telescope is stowed upright protected by the frame. The entire gondola can be moved on the azimuth (yaw) axis by means of the Momentum Transfer Unit, which also acts as the support and attachment point between the gondola and the flight train.

Most of the electronics is housed in three pressurized vessels mounted on the mezzanine, above the MT. On the elevation cage, next to the MT, is attached a fourth vessel. This is the Digital acquisition Pressure Vessel (DPV), which encloses the Digital Acquisition Computer (DAC) that controls the camera. By choosing to house most of the electronics in pressure vessels, we were able to use commercial-grade components better suited for our needs and at a considerably lower cost than space-qualified equivalents. However, commercial-grade electronic components are usually specified for an operational temperature between about 0 °C and 60 °C, which may be exceeded during a sratospheric flight. To overcome this problem we devoted a great effort in thermal design. For example: all the exposed parts were painted white, the mezzanine was protected from direct sunlight by thermal blankets, and the telescope tube was wrapped in more Kapton thermal blankets.