MAXIMA Flight Planning

The flight observation goals include:

• Anisotropy data are the observations of quality regions of the sky.
• Calibration data includes the observations that allow calibration of the instrument output including the conversion to temperature units and to define the parameters of the observations.
• Sunyaev-Zeldovich Effect observations of the SZ effect and other interesting targets such as Galactic emission and interesting sources.
• Engineering data to learn about and characterize the instrument performance.

The first level of flight planning comes from a rough assessment of the experiment goals and capabilities. Once a rough estimate of the flight goals are made then more detail planning can begin. One goal is to select a quality region of the sky.

Selection of a quality region of the sky goes through the following steps:

• Low Dust regions are found by using software that makes maps from the COBE DIRBE and IRAS data. This provides a means to select regions of the sky with both low dust and low dust contrast.
• Radio Source lists are inspected in regions of potential interest. If the region contains too many sources or too bright a radio source, then it is avoided or investigated more carefully.
• Infrared Souce lists are inspected in the regions of potential interest.
• Ephemeris for the moon and planets are inspected.
• Simulations are made to see the range of the data expected for potential scenarios of observations.

Calibration of the MAXIMA receiver consists of determining the conversion from data units to physical units for the receiver data and other things needed to characterize the instrument so that its signature can be removed from the data. The usual steps include observing known signal targets, mapping the beam response using a planet, particularly Jupiter or Saturn, and measuring the overall response in terms of checking sidelobe response and scanning/chopping angles.

There are three targets that are usually considered for the conversion factor calibration:

• The CMB dipole provides a calibration signal of about 3 mK (dTa/dT) which requires rotating the receiver through large angles such as a continuous circle and will in general have a significant contribution from interstellar dust (Galactic) emission.
• Planets particularly Jupiter and Saturn, provide a good, nearly point source, signal. The point-source like nature of the planets requires a good map of the beam and its solid angle for a full calibration.
• A membrane calibrator can be inserted in the beam and was used on the MAX flights.

The beam response and sidelobes are tested both from ground-based measurements and by special observations during flight

• Planets, particularly Jupiter and Saturn, provide a good, nearly point source, signal. The attitude control system is used to make a raster scan about the planet and the detector response then maps out the central beam. The primary necessary information is the ephemeris of the planet.
• An inflight sidelobe test has been to observe a region of the sky as the rotation of the Earth results in a change in elevation angle. Optimally one finds a location and scan direction that does not change (rotate on the sky) significantly for the duration of the test. A suite of programs exist for determining the elevation, azimuth, and scan track direction for a specificed source at a given date and time. These are located in the computer MAXDAT in directory [SOURCE] and some documentation exists in a file called MAX_source.doc.

author George Smoot

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