CREAM Mission Overview

CREAM Members The Cosmic Ray Energetics and Mass (CREAM) experiment was designed and constructed to measure cosmic ray elemental spectra using a series of ultra long duration balloon (ULDB) flights. The goal is to extend direct measurement of cosmic-ray composition to the energies capable of generating gigantic air showers which have been mainly observed on the ground, thereby providing calibration for indirect measurements. The instrument has redundant and complementary charge identification and energy measurement systems capable of precise measurements of elemental spectra for Z = 1 - 26 nuclei over the energy range ~1011 to 1015 eV. Precise measurements of the energy dependance of elemetal spectra at the highest of these energies, where the rigidity-dependant supernova acceleration limit could be reflected in a composition change, provide a key to understanding cosmic ray acceleration and propogation. The instrument includes a Timing Charge Detector (TCD), a Cherenkov Detector (CD), a Transition Radiation Detector (TRD), a Cherenkov Camera (CherCam), a Silicon Charge Detector (SCD), scintillating fiber hodoscopes, and a tungsten-scintillating fiber calorimeter.

The CREAM mission has had six successful flights: (1) 12/16/04 – 1/27/05, (2) 12/16/05 – 1/13/06, (3) 12/19/07 – 1/17/08, (4) 12/19/08 – 1/7/09, and (5) 12/1/09 – 1/8/10, and (6) 12/20/2010 – 12/26/2010 respectively called CREAM-I, -II, -III, -IV, -V, and -VI. A 40 million cubic foot (1.1 million cubic meter) balloon carried each payload to its float altitude between ~38 and ~40 km, with an average atmospheric overburden of ~3.9 g/cm2. A cumulative exposure of ~161 days has been achieved.

Examples of current results are given below:

While waiting for the ISS-CREAM launch, the other balloon payload including a Transition Radiation Detector, which is too large for the JEM-EF envelope, is being prepared for another Antarctic balloon flight in 2016. This so-called Boron And Carbon Cosmic rays in the Upper Stratosphere (BACCUS) mission will focus on the B/C ratio to investigate cosmic ray propagation history.