CAPS Input to a White Paper on Cassini Cruise Science
Instrument Requirements
  1. ICO Phase 2. Require approximately 5 days of operations to verify operation and possible interferences including attitude stability vs. ORS instruments. S/c orientation to include orientation of s/c Z-axis roughly orthogonal to the s/c-sun line so that sensors can view solar wind directly. Data rates: 16, 8, 4, 2, 1, and 0.5 kbps. (All but the 16 and 2 kbps modes need to be tested in ICO 2.)
  2. ICO2 to Jupiter C/A Ė 90 days. Prefer daily turns of CAPS FOV into solar wind viewing direction in order to obtain detailed solar wind spectra. Actual duty cycle will have to be negotiated. The DFPW mode is not suited to solar wind observations because of blockage of the solar wind direction during Earth-point. Monitoring of solar wind for less accurate moment data and for interstellar pickup ions can be done in any orientation. Data rates: detailed distributions (desired ~ 3 % duty cycle): 2 to 16 kbps at average rate of ~ 3 kbps; monitoring function (~97% dc): 0.5 to 2 kbps at average rate of ~0.6 kbps. Average daily rate = 0.67 kbps = 7.2 Mbytes/day.
  3. Jupiter C/A + 90 days to +180 days. Similar requirements as pre-C/A but duty cycle should increase by a factor of at least two to allow some possibility for the chance of observations inside Jupiterís magnetosheath even at fairly long distances from Jupiter. Same requirements for s/c turns to orient Z-axis roughly orthogonal to s/c-sun line. Actual data rate allocation for the Jupiter magnetosheath observations will be managed internally by CAPS based on count-rate triggers. Average daily rate ~ 15 Mbytes/day.
  4. Jupiter C/A + 180 days until approach to Saturnian bow shock region. Same requirements as for period (2) above. Average data rate = 7.2 M bytes/day.
Scientific Justification
  1. ICO 2 is needed to complete checkout, verify new telemetry modes, and set a baseline for solar wind observations at greater radial distances.
  2. Studies include:
    1. contributions to coordinated multipoint measurements of the solar wind;
    2. detailed evolution of the solar wind and features such as shocks, stream boundaries, and CMEís;
    3. ionization, radial distribution and composition of interstellar pickup ions at large radial distances;
    4. evolution of the distribution functions of interstellar ions through pitch angle and energy diffusion;
    5. correlations of the properties of interstellar pickup ions with the properties of the solar wind;
    6. solar wind monitoring in support of ground-based (or early ORS) imaging of Jupiterís aurora.
  3. In addition to the very important continuation of all studies listed in (2) between the orbits of Jupiter and Saturn (a completely unexplored regime in this regard), investigations will include:
    1. detection of the extended Jovian magnetosheath;
    2. detection and characterization of ions escaping from the Jovian magnetosphere;
    3. pickup processes by which Jovian ions are incorporated into the solar wind.
  4. Studies include:
    1. continuation of all objectives listed (2) (except possibly 2f) and (3) to larger distances from the sun and Jupiter;
    2. search for upstream particles escaping from Saturnís bow shock and magnetosphere.