2.1. Mars Surveyor 2001 Rover and Mars Exploration Rover
 The Mars Surveyor 2001 rover was conceived to conduct remote-sensing science and in situ science at specific targets. Additionally, rock cores and soil samples would be acquired and stored on board [Myrick et al., 2000] as a precursor to future sample return missions. Its design was to (1) support the Athena Science Payload, (2) traverse up to 100 m per sol, (3) provide a navigational accuracy of 10% or better, and (4) provide high-speed computational capability and substantial data storage. The Athena Science Payload for that mission consisted of the components listed in Table 1. In addition, that rover was to carry several other camera systems: (1) Navcam atop the mast for navigation, (2) front and rear Hazcams for hazard-avoidance maneuvering, and (3) Bellycams under the rover body to monitor MiniCorer operations.
Table 1. Rover Science Payloads
|Mars Surveyor 2001 Rover||MERa Mission||FIDO|
|High-resolution, color, stereo panoramic imaging||Pancam||Pancam 15 filters 0.4–1.1 μm||Pancam 3 filters 650–855 nm|
|In Situ Analysise|
|Elemental chemical analysis||APXSf||APXS||none|
|Analysis of iron-bearing minerals||Mössbauer Spectrometer||Mössbauer Spectrometer||Mössbauer Spectrometer|
|Precise mineralogical identifications||Raman Spectrometer||none||Raman Spectrometerg|
|Close-up, fine-scale (30 μm/pixel) imaging||Microscopic Imager||Microscopic Imager||Microscopic Imager|
|Rock surface preparation||(MiniCorer)||RATh||Arm-mounted brush or hand-held abrasion tool|
|Rock coring and soil sampling||MiniCorer||none||MiniCoreri|
 The current incarnation of advanced roving on Mars is the Mars Exploration Rover (MER) Project, which plans to launch two rover missions to Mars in 2003 and have them each operating on the surface of Mars in 2004. The MER Mission rovers each carry a modified Athena Science Payload, summarized in Table 1. The basic concept of a rover capable of conducting remote-sensing and in situ science is retained with the new payload composition.
2.2. FIDO Athena Emulation and Payload Requirements
 FIDO is an operational prototype rover, equipped with elements resembling those of the Athena Payload (Table 1). It is used to simulate the complex surface operations expected of an in situ mobile science platform on another planet, focusing on characterization of the scene, identification of rock and soil targets, approaching the targets, and conducting measurements as well as drilling and verification of cores. This last FIDO capability was included to develop Mars Sample Return Mission operations, or, more generally, to develop the operations scenarios needed on rover sample acquisition and return missions.
 The instrument payload on FIDO includes a mast that is stowed on the rover deck when the vehicle is moving and deployed to 1.94 m height for acquisition of stereo imaging and spectral reflectance data. The mast head houses Pancam, a three-band false-color infrared (0.65, 0.74, 0.855 μm) imaging system capable of surveying the terrain in stereo with high spatial resolution for scientific purposes. Pancam imaging provides clues to mineral composition [Arvidson et al., 2002; Jolliff et al., 2002]. These three wavelengths were chosen to yield information on the ferric nature of observed minerals. The Navcam stereo imaging system, which provides low spatial resolution, monochromatic, wide field of view images used for traverse planning, is also included in FIDO's mast head. These systems are similar to those that were intended for the Mars Surveyor 2001 mission [Squyres et al., 2000; Bell et al., 2000b] and that are now planned for the Athena Payload on the MER Missions. However, the angular resolution of the FIDO imaging system is not quite as good as planned for the Athena Payload, and the number and wavelength coverage of the FIDO Pancam bands is less than what is planned for the Athena Pancam. The Infrared Point Spectrometer (IPS) on FIDO is bore-sighted with Navcam and acquires spectral radiance information over wavelengths from 1.3 to 2.5 μm with a spectral resolution of ∼13 cm−1. The IPS can be used in both a point mode and a mode in which a suite or raster of data is acquired to form an image cube. The Miniature Thermal Emission Spectrometer (MiniTES) was to be flown on the Mars Surveyor 2001 Rover and will be flown on the MER Missions, with a wavelength coverage from 5 to 29.5 μm and a spatial resolution choice of either 20 or 8 milliradians [Christensen et al., 2000]. The MiniTES, however, was too expensive to replicate for FIDO. The less expensive IPS was built to simulate joint use of imaging and point hyperspectral data.
 A 4-degree-of-freedom arm is included on the front of the FIDO Rover. The end effector on the arm is the mounting point for a color microscopic imager and an 57Fe Mössbauer Spectrometer. The Mars Surveyor 2001 rover arm would have carried similar instruments for obtaining rock and soil data, with the addition of a calibrated Alpha Proton X-ray Spectrometer (APXS) and a Raman Spectrometer [Wang et al., 2000]. The APXS will not work in Earth's atmosphere because the higher density of terrestrial atmospheric constituents dominates the observed elemental abundance. A Raman Spectrometer was not available for inclusion on FIDO for the field tests.
 The MiniCorer on FIDO is an Athena prototype rock drill directly mounted on the rover body. It is pitched down from its horizontal stow position to acquire a 0.5-cm-diameter by up to 1.7-cm-long core. The equivalent dimensions for the Athena MiniCorer were to be 0.8 × 2.5 cm [Myrick et al., 2000]. Cameras mounted on the underside, or “belly,” of FIDO monitor drill deployment. Similar belly cameras were to be used on the Mars Surveyor 2001 Rover. For FIDO the core can be extracted from the rock and examined with the Microscopic Imager. Once a core's presence is confirmed, it can be either ejected or kept and placed in a caching tube. For the FIDO Rover the Microscopic Imager and Mössbauer Spectrometer can also be placed against rock and soil targets to acquire close-up views and information on iron oxidation state and the mineralogy of iron-bearing phases. For the Mars Surveyor 2001 Rover all three spectrometers and the Microscopic Imager would have been able to be placed against the MiniCorer bit end to make measurements of the rock core tips. The MER Mission rovers will each have a Mössbauer Spectrometer, an Alpha Particle X-ray Spectrometer (still called APXS, but without proton mode), and a Microscopic Imager mounted on a 5-degree-of-freedom arm, along with a drill-like tool for abrading rock surfaces (Table 1).
 Hazard avoidance camera pairs, or Hazcams, on FIDO are located on the front and back of the vehicle to acquire stereo images and terrain maps of the areas to be traversed. Onboard autonomous hazard-avoidance software is used to judge whether obstacles are too high to be successfully traversed. If judged to be a hazard, the software commands the vehicle to search for and implement a traverse around the obstacle while still trying to reach a waypoint designated remotely by the science team. Similar systems were planned for the Mars Surveyor 2001 Rover and will be used on the MER Mission rovers.
 Thus, with the exception of the APXS, the FIDO rover instrument suite provides a useful emulation of the MER Missions' instrument suite and can be used to simulate MER Mission rover operations scenarios with good verisimilitude. In addition, MiniCorer integration with FIDO allows simulation of Mars sample return operations scenarios.