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PRISMA – Mango and Tango in mission operations mode

05. April 2011, 14.30, Ralf Faller, 0 Comment/s
On 14 March 2011, the German Space Operations Center (GSOC) took over operations of PRISMA. Despite my 20 years of service, I must say that even though every mission launch is special, the transfer of operations for an ongoing mission has a very new ‘feel’ about it. PRISMA has been different in many ways. The aim of this mission is to demonstrate various formation flying and rendezvous scenarios at separations of as little as a few metres with satellites Tango and Mango.

It began in 2009 – the Swedish Space Corporation (SSC) took over operations of PRISMA. Despite my 20 years of service, I must say that even though every mission launch is special, the transfer of operations for an ongoing mission has a very new ‘feel’ about it. PRISMA has been different in many ways. The aim of this mission is to demonstrate various formation flying and rendezvous scenarios at separations of as little as a few metres with satellites Tango and Mango.

The objectives of the joint operation fell within the area of responsibility of the Mission Operations division. With the project already prepared and the launch date imminent, a team of specialists from various departments had to be assembled within a short period of time. Their task was to scrutinise the technical and operational requirements and parameters and construct an operational ground segment in very little time. Something normally carried out over the course of several years had to be completed within just a few months. There was only one realistic approach and it was duly selected; it involved taking over large parts of the Swedish ground operations system and making adjustments only where it was strictly necessary. For example, the RAMSES telemetry and command system developed by SSC was used, which meant that the flight procedures had already been established. The DLR station at Weilheim, in southern Germany, and the SSC station at Kiruna, in northern Sweden were selected as ground contacts.

An important part of the preparations involved acquiring the specialist expertise to understand the operational characteristics of both satellites and of their ground system - it was the key to being able to operate both parts of the system safely and reliably. The only way to achieve this was to have the German team present during the final simulations and tests conducted by their Swedish counterparts. From the launch of PRISMA on 15 June 2010 until just before the handover to GSOC, representatives of the future German flight operations team were actively involved in mission operations; German and Swedish specialists worked together in shifts. This made it possible to establish a nine person DLR operations team, which took over from the Swedish team on 15 March 2011 and, for the last three weeks, has been conducting mission operations from Oberpfaffenhofen.

Kontrollraum im DLR

During any one shift, three flight operations engineers work together in the control room. The Flight Director is in charge of operations and makes all the major decisions. The Flight Director is assisted by a specialist in navigation, attitude and orbit control and is responsible for planning and monitoring the experiments and flight manoeuvres. An operator sends the commands to the satellites.

The location of the chosen ground stations and PRISMA's orbit are responsible for the active operational phases at GSOC commencing in the early part of the evening and, in some cases, running right through the night and into the morning. For this reason, an attempt to set up the DLR ground station at Inuvik, in Canada, for PRISMA operations is now being made. This would allow ground station visibility during the daytime at GSOC, moving flight operations to normal office hours. More information about this will come in the next blog post.

Top image: Satellite duo Mango and Tango – separation: 20 metres, altitude: 715 km.  Credit: DLR, CC-BY.

Bottom image: PRISMA control room at DLR Oberpfaffenhofen. Credit: DLR, CC-BY.