Investigation Of The Relative Merits Between DAS And ORSAT For Small Satellite Reentry Analysis

The Glory program is a low-earth satellite that has both Earth and solar science objectives. Glory is required to meet NASA safety standard 1740.14, Guidelines and Assessment Procedures for Limiting Orbital Debris. The post-mission disposal method chosen for Glory is an uncontrolled atmospheric reentry option. Specifically, Guideline 7-1 requires the spacecraft to complete a Reentry Survivability Analysis (RSA). The guideline´s intent is to limit the risk of human casualty by minimizing the surviving components of a spacecraft. Adjustments can be made to the allowable debris casualty area (DCA) depending on reentry year and inclination to keep the risk of human casualty constant (1 in 10,000). Recently Glory underwent a RSA, which was completed using two tools: the debris assessment software (DAS), version 1.5.3, and the object reentry survival analysis tool (ORSAT). The outcome of the RSA is very important to the mission. If the DCA is higher than the allowable, then the mission must pursue one of the possible resolutions that are discussed. If the ORSAT results are the end products that are assessed for policy compliance, then why use DAS at all? If done early DAS analysis can provide an indication of components that should be more carefully analyzed, which can indicate if steps should be taken in the design prior to a potential impact. DAS also helps prepare inputs for ORSAT, which has different input methods, but the information needed is much the same. This paper will strive to explore some of the pitfalls and over-conservatism that may cause difficulties when using the DAS tool and whether the effort is really a necessary task.