A lighter-than-air aircraft includes a gas envelope for containing a buoyant gas, and a solar panel is carried by a predetermined portion of the gas envelope. In one embodiment of the invention, a method for drag and drop object attributes in a GUI can be provided. In the deposition-amount stabilizing process, a plurality of test primary-color toner images are formed by an image forming unit, and a control parameter for the image forming unit are adjusted so as to reduce a difference between each of results of toner deposition amount measurement on the test primary-color toner images and a corresponding target deposition amount. The method includes the provision of at least one lubrication introduction device, at least a portion of which is laden with a lubricant. The CPU 22 of the data receiving apparatus 20 analyses the reproduction control state of the data contained in the data packet based on the simplified reproduction information and the detailed reproduction information contained in the data packet, and controls the reproduction of the data by the action of the media access part 26 according to the analysis result.