Two experiments examined selecting text using a movement sequence of pointing and dragging. Experiment 1 showed that, in the Point-Drag sequence, the pointing time was related to the pointing distance but not to the width of the text to be selected; in contrast, pointing time was related to both the pointing distance and the width of the text in the Point-Click sequence. Experiment 2 demonstrated that both the pointing and dragging times for the Point-Drag sequence were sensitive to the height of the text that was selected. The discussion of the results centers around the application of Fitts' Law to pointing and dragging in a point-drag sequence, proposing that the target for pointing is the leftmost edge of the text to be selected, and the target for dragging is the rightmost edge of the text,

The paper challenges the notion that any Fitts' Law model can be applied generally to human-computer interaction, and proposes instead that applying Fitts' Law requires knowledge of the users' sequence of movements, direction of movement, and typical movement amplitudes as well as target sizes. Two experiments examined a text selection task with sequences of controlled movements (point-click and point-drag). For the point-click sequence, a Fitts' Law model that used the diagonal across the text object in the direction of pointing (rather than the horizontal extent of the text object) as the target size provided the best fit for the pointing time data, whereas for the point-drag sequence, a Fitts' Law model that used the vertical size of the text object as the target size gave the best fit. Dragging times were fitted well by Fitts' Law models that used either the vertical or horizontal size of the terminal character in the text object. Additional results of note were that pointing in the point-click sequence was consistently faster than in the point-drag sequence, and that pointing in either sequence was consistently faster than dragging. The discussion centres around the need to define task characteristics before applying Fitts' Law to an interface design or analysis, analyses of pointing and of dragging, and implications for interface design.

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Excessive noise can lead to decrements in performance, impaired verbal communication, fatigue, and hearing damage. On the STS-40/SLS-1 mission noise levels were evaluated through the use of a questionnaire and two objective measures−in-flight sound level measurements and pre- and post-flight crew audiometry tests. Sound level meter measurements suggested that noise levels in Spacelab during nominal operations were approximately 70 dB (A-weighted). This is in excess of the current acoustic specification of 59 dB (A-weighted). Noise measurements conducted in the Orbiter did not exceed current Shuttle standards. Crewmembers recommended that noise levels be reduced. Post-flight audiometry tests indicated that transient decreases in hearing ability had taken place during the mission. The average decrease in hearing level of 4.34 dB was statistically significant. Crewmembers noted that sleep, concentration, and relaxation were negatively impacted by high noise levels. Communication was also hampered. The higher than desirable noise levels in Spacelab were attributed to flight specific payloads for which acoustic waivers were granted. It is recommended that current noise levels be reduced in Spacelab and the Orbiter Middeck. Levels of NC 50 are recommended in areas where speech communication is required, and NC 40 in sleep areas−in accordance with current Space Station Freedom standards. [This research was supported by the National Aeronautics and Space Administration under Contract No. NAS9-17900.]

Remotely controlled devices will be used extensively to support Space Station Freedom on-orbit assembly, maintenance, and payloads. These include crane-type or remote manipulator systems (RMS), dexterous robots, and remotely-piloted free flyers. A hand controller evaluation process has been established at NASA's Johnson Space Center to determine the appropriate hand controller configurations required to support these devices. Three test facilities include dynamic computer simulations, kinematic computer simulations, and physical simulations. The dynamic simulator supported a rate-controlled RMS and a free flyer. The kinematic simulator supported a rate-controlled RMS and a rate or position-controlled dexterous manipulator. The physical simulator supported a rate, position, or force-reflecting dexterous manipulator. Standard interfaces were developed to evaluate six different hand controllers in all three facilities. The hand controllers included six degree-of-freedom (DOF) position and rate mini-master and joystick controllers, and three-DOF rate controllers. There were six tasks and four non-astronaut subjects per task. All six controllers were tested for each task. Six astronauts then completed all tasks using all controllers for each task. Data collected included task performance data, subjective comments, and anthropometric data. The results of these evaluations were then used to make hand controller configuration recommendations to the Space Station Freedom Program.