STS-103 mission specialist John M. Grunsfeld attached to a workstation on the RMS arm and payload commander Steven L. Smith free-floating perform a changeout of the Rate Sensor Units RSU in one of the bays of -V3 plane of the Hubble Space Telescope HST. This repair was performed during the first of three extravehicular activities EVAs of the mission. Grunsfeld is distinguished by having no marks on his EMU and Smith is distinguished by the red strip on the pants of his EMU.
