PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "T. Farnham 2006-07-07" RECORD_TYPE = STREAM OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "SDU" INSTRUMENT_ID = "SRC" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = "SAMPLE RETURN CAPSULE" INSTRUMENT_TYPE = "DUST SAMPLE COLLECTOR" INSTRUMENT_DESC = " The descriptions in this file were written by Tony Farnham using information from the ``Stardust Mission Plan document'' (used by permission from the Stardust project). Instrument description ----------------------- The Sample Return Capsule (SRC) was a system for non-destructively collecting cometary and interstellar dust particles, then storing the samples and returning them to the Earth for detailed analysis. The Sample Return Capsule was about a meter in diameter, and opened like a clamshell, allowing the collecting grid to be deployed into the dust stream to collect samples. The SRC was mounted along the negative -x--axis of the Stardust spacecraft. It consisted of four main components: the sample collector, the aeroshell (backshell and heat shield), the parachute system, and the avionics. Sample CollectorCOllector ---------------- The sample collector was a passive system for collecting dust grains. It consisted of an aluminum grid encasing multiple microporous silica aerogel blocks that acted as the dust collectors. The grid array was exposed to a stream of dust particles, which were gradually slowed by the low-density aerogel. The aerogel dissipated the kinetic energy of the particles so they were not destroyed during the collection process. Graded density media werewas used to give even lower density for the initial impact. The aerogel collector grid allowed collection from both sides. One side of the collector (facing the +x direction) was used to collect samples during the comet encounter and the opposite side was used for interstellar dust collection. Each side of the collector contained a total of 1000 cm^2 of useful collecting area. After the samples were obtained, the collector grid could fold up into a compact configuration in the sample return capsule. Stowage of the collector was achieved by first folding the collector grid onto the boom via the wrist joint and then folding the boom/collector into the SRC canister via the shoulder joint. In addition to allowing the collector grid to fold up into the SRC, where it was protected, this deployment mechanism was the key for maximizing the amount of time available for the capture of interstellar dust particles. The mechanism allowed the collector to be steered via the wrist joint about the spacecraft y-axis toward the negative -z--axis. The collector field-of-view remained unobstructed by the SRC backshield for 51 degrees of this motion, half the grid was in shadow at 63 degrees, and all of the grid was in shadow at 75 degrees. (Note that for the shadow definition, the interstellar particle (ISP) stream is assumed to be incoming perpendicular to the aerogel grid.) It is worth noting that the collector field-of-view would remain completely unobstructed for 65 degrees of the motion should the shoulder joint be used during interstellar dust particle collection. However, usage of the shoulder joint with the collector fully deployed was considered to be an unnecessary risk. Aeroshell --------- The aeroshell was used to protect the SRC during the cruise phases and during re-entry into the Earth's atmosphere. During re-entry, the aeroshell removed dissipated over 99 percent of the initial kinetic energy of the vehicle and protected the sample canister against the extreme aerodynamic heating of atmospheric entry. The heat shield was a 60 degree half angle blunt cone made of a graphite/epoxy composite covered with a thermal protection system. Ablative material was also applied to the backshell to protect the capsule from the effects of recirculation flow. Parachute System ---------------- During the entry and descent phases, a G-switch initiated timer with What is a G-switch? A "gravity" switch? backup pressure sensors provided the required parachute deployment timing. The parachute system incorporated a drogue and main chute into a single parachute canister. The parachute canister contained a mortar tube that held the drogue chute. A gas cartridge was housed outside the canister and was used to pressurize the mortar tube and expel the drogue chute. The drogue chute was used to stabilize the descending SRC through the transonic and subsonic atmospheric regimes. The drogue was discarded using one of two redundant cutters, extracting the main chute as it moves away from the SRC. Upon ground impact, a cutter in the riser of the main chute was commanded by a G-switch, separating the main chute from the SRC to prevent surface winds from dragging the SRC across the ground. Avionics -------- The avionics design included a UHF locator beacon used as an SRC location aid for the ground recovery team. The beacon was activated upon main chute deployment. It was powered by a set of primary cell lithium sulfur dioxide batteries, which had enough capacity to operate the beacon for 40 hours. Additional SRC tracking was provided by skin tracking from two C-band radar sites at the Utah Test and Training Range (UTTR) landing site. A mylar target mounted on the main chute provides an equivalent one square meter of radar cross section. Earth Return Sequence --------------------- On January 15, 2006, the Sample Return Capsule returned to the Earth. Prior to separation, the spacecraft was placed at the separation attitude and the SRC was spun up using a spin release mechanism. This provided the spin stabilization that the SRC required for successful atmospheric entry. After the SRC separated, the spacecraft executed a divert maneuver, to put it into a heliocentric orbit. The SRC entered the atmosphere at 09:57 UTC on January 15, 2006. The SRC continued to free-fall to an altitude of about 3 km, at which point the parachute deployed, allowing the SRC to safely land safely at the Utah Test and Training Range. It was recovered and transported to a staging area at UTTR for retrieval of the sample canister, which was then be transported to the planetary materials curatorial facility at Johnson Space Center. " END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "N/A" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END