Downpatrick Crown Court Judge David Smyth QC told 34-year-old Richard Chilvers, that despite his remorse and shame, he had to be jailed as the public interest demanded the market and trade in such images be dealt with.
However, given his guilty plea and substantial mitigation, including the fact that Chilvers, orphaned in the Kegworth air disaster, was later sexually abused by a drunken brother in-law, Judge Smyth said he would reduce his two-year sentence to 17 months.
This would be split between five months jail, followed by 12 months on supervised licenced parole.
Chilvers, whose address was given as Tennant Street PSNI Station in Belfast, pleaded guilty to 22 charges involving 985 images of children being sexually abused.
They were found mainly on an external computer hard drive following his arrest last June.
A total of 16 charges related to downloading the images, four to possession, and two referred to his distributing two of the images.
This defendant, from the first moment he was approached by the authorities, admitted his culpability for which he hangs his head in shame.
Denis Maloney, defence solicitor-advocate
Judge Smyth said the former constable was not regarded as a risk to the public or youngsters and had he not told police about the external hard drive he would have escaped detection, which was a further sign of his guilty conscience.
Prosecution lawyer David McDowell said when police arrived at his home, Chilvers "immediately acknowledged" why they had come, telling officers: "My life is over. I can't handle this".
The lawyer added that the bulk of the images were "movies" and when a sample of 36 were analysed, 25 were found to be in the more serious higher category four, while eight were in category two and three were from category three.
Mr McDowell said Chilvers, a victim of sexual abuse himself, made full and frank admissions and that he regarded being uncovered as "taking a weight off his shoulders".
The lawyer also revealed that while the former policeman had coached an under-12 basket ball team, there was no untoward behaviour on his part, nor had any complaint ever been made against him.
Defence solicitor-advocate Denis Maloney of Donnelly and Wall solicitors said that firstly it had to be acknowledged that "behind every image there is a victim and every victim was a child".
He added: "One can say quite clearly to the court that this defendant knows only too well what he did was legally, morally, and in every sense of the word, wrong", but that he posed no direct danger to young people either in the past, and certainly not in the future.
Chilvers, he said, was someone who had served the community as a police officer and as a basketball coach, but who had now lost everything, friends, reputation and career.
Mr Maloney said that following the death of his parents, he was taken in and cared for by his loving sister.
However, until this case was uncovered, she was unaware that her husband, who has since died, had been abusing her young brother from he was 12.
This in turn had led to Chilvers questioning his own sexuality and finally to these offences.
Chilvers "was always expecting police to come to his door at some point", and when they did he made full and frank admissions, without which he would not have been prosecuted.
A detective said that without Chilvers' help, it would also have cost the authorities thousands of pounds in specialist work on his computer hard drives.